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<title>第 15 章 正则表达式 | R编程与作图</title>
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<nav aria-label="Table of contents"><h2>Table of contents</h2>
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<li><a class="" href="index.html">前言</a></li>
<li class="book-part">R编程基础</li>
<li><a class="" href="baseR-intro-ds.html"><span class="header-section-number">1</span> R语言介绍及资料推荐</a></li>
<li><a class="" href="baseR-install.html"><span class="header-section-number">2</span> 安装与环境配置</a></li>
<li><a class="" href="baseR-objects.html"><span class="header-section-number">3</span> 对象</a></li>
<li><a class="" href="baseR-vectors.html"><span class="header-section-number">4</span> 向量</a></li>
<li><a class="" href="baseR-data-structure.html"><span class="header-section-number">5</span> 数据结构</a></li>
<li><a class="" href="baseR-operators.html"><span class="header-section-number">6</span> 运算符及向量运算</a></li>
<li><a class="" href="baseR-functions.html"><span class="header-section-number">7</span> 函数</a></li>
<li><a class="" href="baseR-functions-adv.html"><span class="header-section-number">8</span> 函数应用</a></li>
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<li class="book-part">数据读入与处理</li>
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<li><a class="" href="tidyverse-dplyr-apply.html"><span class="header-section-number">12</span> dplyr进阶</a></li>
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<li><a class="active" href="tidyverse-stringr.html"><span class="header-section-number">15</span> 正则表达式</a></li>
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<li><a class="" href="tidyverse-ggplot2-from-layer-to-geom.html"><span class="header-section-number">25</span> ggplot2之从图层到几何形状</a></li>
<li><a class="" href="tidyverse-ggplot2-colors.html"><span class="header-section-number">26</span> ggplot2之数据可视化中的配色</a></li>
<li><a class="" href="tidyverse-ggplot2-override-aes.html"><span class="header-section-number">27</span> ggplot2之控制图例的外观</a></li>
<li><a class="" href="tidyverse-ggplot2-aes-eval.html"><span class="header-section-number">28</span> ggplot2之延迟映射</a></li>
<li><a class="" href="tidyverse-ggplot2-academic.html"><span class="header-section-number">29</span> ggplot2之科研数据可视化</a></li>
<li><a class="" href="tidyverse-ggplot2-gganimate.html"><span class="header-section-number">30</span> ggplot2之让你的数据动起来</a></li>
<li><a class="" href="tidyverse-ggplot2-pass-function-as-parameters.html"><span class="header-section-number">31</span> ggplot2中传递函数作为参数值</a></li>
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<li><a class="" href="eda-practice.html"><span class="header-section-number">33</span> 一天一练</a></li>
<li class="book-part">GO/KEGG富集分析</li>
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</header><main class="col-sm-12 col-md-9 col-lg-7" id="content"><div id="tidyverse-stringr" class="section level1" number="15">
<h1>
<span class="header-section-number">第 15 章</span> 正则表达式<a class="anchor" aria-label="anchor" href="#tidyverse-stringr"><i class="fas fa-link"></i></a>
</h1>
<div class="sourceCode" id="cb627"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="kw"><a href="https://rdrr.io/r/base/library.html">library</a></span><span class="op">(</span><span class="va"><a href="https://tidyverse.tidyverse.org">tidyverse</a></span><span class="op">)</span></span>
<span><span class="kw"><a href="https://rdrr.io/r/base/library.html">library</a></span><span class="op">(</span><span class="va"><a href="https://stringr.tidyverse.org">stringr</a></span><span class="op">)</span></span></code></pre></div>
<div id="问题" class="section level2" number="15.1">
<h2>
<span class="header-section-number">15.1</span> 问题<a class="anchor" aria-label="anchor" href="#%E9%97%AE%E9%A2%98"><i class="fas fa-link"></i></a>
</h2>
<p>这是一份关于地址信息的数据</p>
<pre><code>## # A tibble: 8 × 2
## No address
## <int> <chr>
## 1 1 Sichuan Univ, Coll Chem
## 2 2 Sichuan Univ, Coll Elect Engn
## 3 3 Sichuan Univ, Dept Phys
## 4 4 Sichuan Univ, Coll Life Sci
## 5 6 Sichuan Univ, Food Engn
## 6 7 Sichuan Univ, Coll Phys
## 7 8 Sichuan Univ, Sch Business
## 8 9 Wuhan Univ, Mat Sci</code></pre>
<p><strong>问题</strong>：如何提取<code>Sichuan Univ</code>后面的学院？这需要用到正则表达式的知识。</p>
</div>
<div id="什么是正则表达式" class="section level2" number="15.2">
<h2>
<span class="header-section-number">15.2</span> 什么是正则表达式<a class="anchor" aria-label="anchor" href="#%E4%BB%80%E4%B9%88%E6%98%AF%E6%AD%A3%E5%88%99%E8%A1%A8%E8%BE%BE%E5%BC%8F"><i class="fas fa-link"></i></a>
</h2>
<p>我们在word文档或者excel中，经常使用查找和替换, 然而有些情况，word是解决不了的，比如</p>
<ul>
<li>条件搜索
<ul>
<li>统计文中，前面有 “data”, “computer” or “statistical” 的 “analysis”，这个单词的个数</li>
<li>找出文中重复的单词，比如“we love love you”</li>
</ul>
</li>
<li>拼写检查
<ul>
<li>电话号码（邮件，密码等）是否正确格式</li>
<li>日期书写的规范与统一</li>
</ul>
</li>
<li>提取信息
<ul>
<li>提取文本特定位置的数据</li>
</ul>
</li>
<li>文本挖掘
<ul>
<li>非结构化的提取成结构化</li>
</ul>
</li>
</ul>
<p>这个时候就需要用到正则表达式（Regular Expression），这一强大、便捷、高效的文本处理工具。那么，什么是正则表达式呢？简单点说，正则表达式是处理字符串的。复杂点说，正则表达式描述了一种字符串匹配的模式（pattern），通常被用来检索、替换那些符合某个模式(规则)的文本。这种固定的格式的文本，生活中常见的有电话号码、网络地址、邮件地址和日期格式等等。</p>
<p>正则表达式并不是R语言特有的，事实上，几乎所有程序语言都支持正则表达式 (e.g. Perl, Python, Java, Ruby, etc).</p>
<p>R 语言中很多函数都需要使用正则表达式，然而正则表达式不太好学。幸运的是，大神Hadley Wickham开发的stringr包让正则表达式简单易懂，因此今天我们就介绍这个包。本章的内容与《R for data science》第10章基本一致。本章目的教大家写<strong>简单的</strong>正则表示式就行了。</p>
</div>
<div id="字符串基础" class="section level2" number="15.3">
<h2>
<span class="header-section-number">15.3</span> 字符串基础<a class="anchor" aria-label="anchor" href="#%E5%AD%97%E7%AC%A6%E4%B8%B2%E5%9F%BA%E7%A1%80"><i class="fas fa-link"></i></a>
</h2>
<div id="字符串长度" class="section level3" number="15.3.1">
<h3>
<span class="header-section-number">15.3.1</span> 字符串长度<a class="anchor" aria-label="anchor" href="#%E5%AD%97%E7%AC%A6%E4%B8%B2%E9%95%BF%E5%BA%A6"><i class="fas fa-link"></i></a>
</h3>
<p>想获取字符串的长度，可以使用<code><a href="https://stringr.tidyverse.org/reference/str_length.html">str_length()</a></code>函数</p>
<div class="sourceCode" id="cb629"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_length.html">str_length</a></span><span class="op">(</span><span class="st">"R for data science"</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [1] 18</code></pre>
<p>字符串向量，也适用</p>
<div class="sourceCode" id="cb631"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_length.html">str_length</a></span><span class="op">(</span><span class="fu"><a href="https://rdrr.io/r/base/c.html">c</a></span><span class="op">(</span><span class="st">"a"</span>, <span class="st">"R for data science"</span>, <span class="cn">NA</span><span class="op">)</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [1] 1 18 NA</code></pre>
<p>数据框里配合dplyr函数，同样很方便</p>
<div class="sourceCode" id="cb633"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="fu"><a href="https://rdrr.io/r/base/data.frame.html">data.frame</a></span><span class="op">(</span></span>
<span> x <span class="op">=</span> <span class="fu"><a href="https://rdrr.io/r/base/c.html">c</a></span><span class="op">(</span><span class="st">"a"</span>, <span class="st">"R for data science"</span>, <span class="cn">NA</span><span class="op">)</span></span>
<span><span class="op">)</span> <span class="op"><a href="https://magrittr.tidyverse.org/reference/pipe.html">%>%</a></span></span>
<span> <span class="fu"><a href="https://dplyr.tidyverse.org/reference/mutate.html">mutate</a></span><span class="op">(</span>y <span class="op">=</span> <span class="fu"><a href="https://stringr.tidyverse.org/reference/str_length.html">str_length</a></span><span class="op">(</span><span class="va">x</span><span class="op">)</span><span class="op">)</span></span></code></pre></div>
<pre><code>## x y
## 1 a 1
## 2 R for data science 18
## 3 <NA> NA</code></pre>
</div>
<div id="字符串组合" class="section level3" number="15.3.2">
<h3>
<span class="header-section-number">15.3.2</span> 字符串组合<a class="anchor" aria-label="anchor" href="#%E5%AD%97%E7%AC%A6%E4%B8%B2%E7%BB%84%E5%90%88"><i class="fas fa-link"></i></a>
</h3>
<p>把字符串拼接在一起，使用 <code><a href="https://stringr.tidyverse.org/reference/str_c.html">str_c()</a></code> 函数</p>
<div class="sourceCode" id="cb635"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_c.html">str_c</a></span><span class="op">(</span><span class="st">"x"</span>, <span class="st">"y"</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [1] "xy"</code></pre>
<p>把字符串拼接在一起，可以设置中间的间隔</p>
<div class="sourceCode" id="cb637"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_c.html">str_c</a></span><span class="op">(</span><span class="st">"x"</span>, <span class="st">"y"</span>, sep <span class="op">=</span> <span class="st">", "</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [1] "x, y"</code></pre>
<div class="sourceCode" id="cb639"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_c.html">str_c</a></span><span class="op">(</span><span class="fu"><a href="https://rdrr.io/r/base/c.html">c</a></span><span class="op">(</span><span class="st">"x"</span>, <span class="st">"y"</span>, <span class="st">"z"</span><span class="op">)</span>, sep <span class="op">=</span> <span class="st">", "</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [1] "x" "y" "z"</code></pre>
<p>是不是和你想象的不一样，那就<code><a href="https://stringr.tidyverse.org/reference/str_c.html">?str_c</a></code>，或者试试这个</p>
<div class="sourceCode" id="cb641"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_c.html">str_c</a></span><span class="op">(</span><span class="fu"><a href="https://rdrr.io/r/base/c.html">c</a></span><span class="op">(</span><span class="st">"x"</span>, <span class="st">"y"</span>, <span class="st">"z"</span><span class="op">)</span>, <span class="fu"><a href="https://rdrr.io/r/base/c.html">c</a></span><span class="op">(</span><span class="st">"x"</span>, <span class="st">"y"</span>, <span class="st">"z"</span><span class="op">)</span>, sep <span class="op">=</span> <span class="st">", "</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [1] "x, x" "y, y" "z, z"</code></pre>
<p>用在数据框里</p>
<div class="sourceCode" id="cb643"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="fu"><a href="https://rdrr.io/r/base/data.frame.html">data.frame</a></span><span class="op">(</span></span>
<span> x <span class="op">=</span> <span class="fu"><a href="https://rdrr.io/r/base/c.html">c</a></span><span class="op">(</span><span class="st">"I"</span>, <span class="st">"love"</span>, <span class="st">"you"</span><span class="op">)</span>,</span>
<span> y <span class="op">=</span> <span class="fu"><a href="https://rdrr.io/r/base/c.html">c</a></span><span class="op">(</span><span class="st">"you"</span>, <span class="st">"like"</span>, <span class="st">"me"</span><span class="op">)</span></span>
<span><span class="op">)</span> <span class="op"><a href="https://magrittr.tidyverse.org/reference/pipe.html">%>%</a></span></span>
<span> <span class="fu"><a href="https://dplyr.tidyverse.org/reference/mutate.html">mutate</a></span><span class="op">(</span>z <span class="op">=</span> <span class="fu"><a href="https://stringr.tidyverse.org/reference/str_c.html">str_c</a></span><span class="op">(</span><span class="va">x</span>, <span class="va">y</span>, sep <span class="op">=</span> <span class="st">"|"</span><span class="op">)</span><span class="op">)</span></span></code></pre></div>
<pre><code>## x y z
## 1 I you I|you
## 2 love like love|like
## 3 you me you|me</code></pre>
<p>使用collapse选项，是先组合，然后再转换成单个字符串，大家对比下</p>
<div class="sourceCode" id="cb645"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_c.html">str_c</a></span><span class="op">(</span><span class="fu"><a href="https://rdrr.io/r/base/c.html">c</a></span><span class="op">(</span><span class="st">"x"</span>, <span class="st">"y"</span>, <span class="st">"z"</span><span class="op">)</span>, <span class="fu"><a href="https://rdrr.io/r/base/c.html">c</a></span><span class="op">(</span><span class="st">"a"</span>, <span class="st">"b"</span>, <span class="st">"c"</span><span class="op">)</span>, sep <span class="op">=</span> <span class="st">"|"</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [1] "x|a" "y|b" "z|c"</code></pre>
<div class="sourceCode" id="cb647"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_c.html">str_c</a></span><span class="op">(</span><span class="fu"><a href="https://rdrr.io/r/base/c.html">c</a></span><span class="op">(</span><span class="st">"x"</span>, <span class="st">"y"</span>, <span class="st">"z"</span><span class="op">)</span>, <span class="fu"><a href="https://rdrr.io/r/base/c.html">c</a></span><span class="op">(</span><span class="st">"a"</span>, <span class="st">"b"</span>, <span class="st">"c"</span><span class="op">)</span>, collapse <span class="op">=</span> <span class="st">"|"</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [1] "xa|yb|zc"</code></pre>
</div>
<div id="字符串取子集" class="section level3" number="15.3.3">
<h3>
<span class="header-section-number">15.3.3</span> 字符串取子集<a class="anchor" aria-label="anchor" href="#%E5%AD%97%E7%AC%A6%E4%B8%B2%E5%8F%96%E5%AD%90%E9%9B%86"><i class="fas fa-link"></i></a>
</h3>
<p>截取字符串的一部分，需要指定截取的开始位置和结束位置</p>
<div class="sourceCode" id="cb649"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">x</span> <span class="op"><-</span> <span class="fu"><a href="https://rdrr.io/r/base/c.html">c</a></span><span class="op">(</span><span class="st">"Apple"</span>, <span class="st">"Banana"</span>, <span class="st">"Pear"</span><span class="op">)</span></span>
<span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_sub.html">str_sub</a></span><span class="op">(</span><span class="va">x</span>, <span class="fl">1</span>, <span class="fl">3</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [1] "App" "Ban" "Pea"</code></pre>
<p>开始位置和结束位置如果是负整数，就表示位置是从后往前数，比如下面这段代码，截取倒数第3个至倒数第1个位置上的字符串</p>
<div class="sourceCode" id="cb651"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">x</span> <span class="op"><-</span> <span class="fu"><a href="https://rdrr.io/r/base/c.html">c</a></span><span class="op">(</span><span class="st">"Apple"</span>, <span class="st">"Banana"</span>, <span class="st">"Pear"</span><span class="op">)</span></span>
<span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_sub.html">str_sub</a></span><span class="op">(</span><span class="va">x</span>, <span class="op">-</span><span class="fl">3</span>, <span class="op">-</span><span class="fl">1</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [1] "ple" "ana" "ear"</code></pre>
<p>也可以进行赋值，如果该位置上有字符，就用新的字符替换旧的字符</p>
<div class="sourceCode" id="cb653"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">x</span> <span class="op"><-</span> <span class="fu"><a href="https://rdrr.io/r/base/c.html">c</a></span><span class="op">(</span><span class="st">"Apple"</span>, <span class="st">"Banana"</span>, <span class="st">"Pear"</span><span class="op">)</span></span>
<span><span class="va">x</span></span></code></pre></div>
<pre><code>## [1] "Apple" "Banana" "Pear"</code></pre>
<div class="sourceCode" id="cb655"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_sub.html">str_sub</a></span><span class="op">(</span><span class="va">x</span>, <span class="fl">1</span>, <span class="fl">1</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [1] "A" "B" "P"</code></pre>
<div class="sourceCode" id="cb657"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_sub.html">str_sub</a></span><span class="op">(</span><span class="va">x</span>, <span class="fl">1</span>, <span class="fl">1</span><span class="op">)</span> <span class="op"><-</span> <span class="st">"Q"</span></span>
<span><span class="va">x</span></span></code></pre></div>
<pre><code>## [1] "Qpple" "Qanana" "Qear"</code></pre>
</div>
</div>
<div id="使用正则表达式进行模式匹配" class="section level2" number="15.4">
<h2>
<span class="header-section-number">15.4</span> 使用正则表达式进行模式匹配<a class="anchor" aria-label="anchor" href="#%E4%BD%BF%E7%94%A8%E6%AD%A3%E5%88%99%E8%A1%A8%E8%BE%BE%E5%BC%8F%E8%BF%9B%E8%A1%8C%E6%A8%A1%E5%BC%8F%E5%8C%B9%E9%85%8D"><i class="fas fa-link"></i></a>
</h2>
<p>正则表示式慢慢会呈现了</p>
<div id="基础匹配" class="section level3" number="15.4.1">
<h3>
<span class="header-section-number">15.4.1</span> 基础匹配<a class="anchor" aria-label="anchor" href="#%E5%9F%BA%E7%A1%80%E5%8C%B9%E9%85%8D"><i class="fas fa-link"></i></a>
</h3>
<p><code><a href="https://stringr.tidyverse.org/reference/str_view.html">str_view()</a></code> 是查看string是否匹配pattern，如果匹配，就高亮显示</p>
<div class="sourceCode" id="cb659"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">x</span> <span class="op"><-</span> <span class="fu"><a href="https://rdrr.io/r/base/c.html">c</a></span><span class="op">(</span><span class="st">"apple"</span>, <span class="st">"banana"</span>, <span class="st">"pear"</span><span class="op">)</span></span>
<span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_view.html">str_view</a></span><span class="op">(</span>string <span class="op">=</span> <span class="va">x</span>, pattern <span class="op">=</span> <span class="st">"an"</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [2] │ b<an><an>a</code></pre>
<p>有时候，我们希望在字符<code>a</code>前后都有字符（即，a处在两字符中间，如rap, bad, sad, wave，spear等等）</p>
<div class="sourceCode" id="cb661"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">x</span> <span class="op"><-</span> <span class="fu"><a href="https://rdrr.io/r/base/c.html">c</a></span><span class="op">(</span><span class="st">"apple"</span>, <span class="st">"banana"</span>, <span class="st">"pear"</span><span class="op">)</span></span>
<span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_view.html">str_view</a></span><span class="op">(</span><span class="va">x</span>, <span class="st">".a."</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [2] │ <ban>ana
## [3] │ p<ear></code></pre>
<p>这里的<code>.</code> 代表任意字符。如果向表达.本身呢？</p>
<div class="sourceCode" id="cb663"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="fu"><a href="https://rdrr.io/r/base/c.html">c</a></span><span class="op">(</span><span class="st">"s.d"</span><span class="op">)</span> <span class="op"><a href="https://magrittr.tidyverse.org/reference/pipe.html">%>%</a></span></span>
<span> <span class="fu"><a href="https://stringr.tidyverse.org/reference/str_view.html">str_view</a></span><span class="op">(</span><span class="st">"."</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [1] │ <s><.><d></code></pre>
<div class="sourceCode" id="cb665"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="fu"><a href="https://rdrr.io/r/base/c.html">c</a></span><span class="op">(</span><span class="st">"s.d"</span><span class="op">)</span> <span class="op"><a href="https://magrittr.tidyverse.org/reference/pipe.html">%>%</a></span></span>
<span> <span class="fu"><a href="https://stringr.tidyverse.org/reference/str_view.html">str_view</a></span><span class="op">(</span><span class="st">"\\."</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [1] │ s<.>d</code></pre>
</div>
<div id="锚点" class="section level3" number="15.4.2">
<h3>
<span class="header-section-number">15.4.2</span> 锚点<a class="anchor" aria-label="anchor" href="#%E9%94%9A%E7%82%B9"><i class="fas fa-link"></i></a>
</h3>
<p>希望<code>a</code>是字符串的开始</p>
<div class="sourceCode" id="cb667"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">x</span> <span class="op"><-</span> <span class="fu"><a href="https://rdrr.io/r/base/c.html">c</a></span><span class="op">(</span><span class="st">"apple"</span>, <span class="st">"banana"</span>, <span class="st">"pear"</span><span class="op">)</span></span>
<span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_view.html">str_view</a></span><span class="op">(</span><span class="va">x</span>, <span class="st">"^a"</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [1] │ <a>pple</code></pre>
<p>希望<code>a</code>是一字符串的末尾</p>
<div class="sourceCode" id="cb669"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">x</span> <span class="op"><-</span> <span class="fu"><a href="https://rdrr.io/r/base/c.html">c</a></span><span class="op">(</span><span class="st">"apple"</span>, <span class="st">"banana"</span>, <span class="st">"pear"</span><span class="op">)</span></span>
<span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_view.html">str_view</a></span><span class="op">(</span><span class="va">x</span>, <span class="st">"a$"</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [2] │ banan<a></code></pre>
<div class="sourceCode" id="cb671"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">x</span> <span class="op"><-</span> <span class="fu"><a href="https://rdrr.io/r/base/c.html">c</a></span><span class="op">(</span><span class="st">"apple pie"</span>, <span class="st">"apple"</span>, <span class="st">"apple cake"</span><span class="op">)</span></span>
<span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_view.html">str_view</a></span><span class="op">(</span><span class="va">x</span>, <span class="st">"^apple$"</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [2] │ <apple></code></pre>
</div>
<div id="字符类与字符选项" class="section level3" number="15.4.3">
<h3>
<span class="header-section-number">15.4.3</span> 字符类与字符选项<a class="anchor" aria-label="anchor" href="#%E5%AD%97%E7%AC%A6%E7%B1%BB%E4%B8%8E%E5%AD%97%E7%AC%A6%E9%80%89%E9%A1%B9"><i class="fas fa-link"></i></a>
</h3>
<p>前面提到，<code>.</code>匹配任意字符，事实上还有很多这种<strong>特殊含义</strong>的字符：</p>
<ul>
<li>
<code>\d</code>: matches any digit.</li>
<li>
<code>\s</code>: matches any whitespace (e.g. space, tab, newline).</li>
<li>
<code>[abc]</code>: matches a, b, or c.</li>
<li>
<code>[^abc]</code>: matches anything except a, b, or c.</li>
</ul>
<div class="sourceCode" id="cb673"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_view.html">str_view</a></span><span class="op">(</span><span class="fu"><a href="https://rdrr.io/r/base/c.html">c</a></span><span class="op">(</span><span class="st">"grey"</span>, <span class="st">"gray"</span><span class="op">)</span>, <span class="st">"gr[ea]y"</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [1] │ <grey>
## [2] │ <gray></code></pre>
</div>
<div id="重复" class="section level3" number="15.4.4">
<h3>
<span class="header-section-number">15.4.4</span> 重复<a class="anchor" aria-label="anchor" href="#%E9%87%8D%E5%A4%8D"><i class="fas fa-link"></i></a>
</h3>
<p>控制匹配次数:</p>
<ul>
<li>
<code>?</code>: 0 or 1</li>
<li>
<code>+</code>: 1 or more</li>
<li>
<code>*</code>: 0 or more</li>
</ul>
<div class="sourceCode" id="cb675"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">x</span> <span class="op"><-</span> <span class="st">"Roman numerals: MDCCCLXXXVIII"</span></span>
<span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_view.html">str_view</a></span><span class="op">(</span><span class="va">x</span>, <span class="st">"CC?"</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [1] │ Roman numerals: MD<CC><C>LXXXVIII</code></pre>
<div class="sourceCode" id="cb677"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_view.html">str_view</a></span><span class="op">(</span><span class="va">x</span>, <span class="st">"X+"</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [1] │ Roman numerals: MDCCCL<XXX>VIII</code></pre>
<p>控制匹配次数:</p>
<ul>
<li>
<code>{n}</code>: exactly n</li>
<li>
<code>{n,}</code>: n or more</li>
<li>
<code>{,m}</code>: at most m</li>
<li>
<code>{n,m}</code>: between n and m</li>
</ul>
<div class="sourceCode" id="cb679"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">x</span> <span class="op"><-</span> <span class="st">"Roman numerals: MDCCCLXXXVIII"</span></span>
<span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_view.html">str_view</a></span><span class="op">(</span><span class="va">x</span>, <span class="st">"C{2}"</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [1] │ Roman numerals: MD<CC>CLXXXVIII</code></pre>
<div class="sourceCode" id="cb681"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_view.html">str_view</a></span><span class="op">(</span><span class="va">x</span>, <span class="st">"C{2,}"</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [1] │ Roman numerals: MD<CCC>LXXXVIII</code></pre>
<div class="sourceCode" id="cb683"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_view.html">str_view</a></span><span class="op">(</span><span class="va">x</span>, <span class="st">"C{2,3}"</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [1] │ Roman numerals: MD<CCC>LXXXVIII</code></pre>
<ul>
<li>默认的情况，<code>*</code>, <code>+</code> 匹配都是<strong>贪婪</strong>的，也就是它会尽可能的匹配更多</li>
<li>如果想让它不贪婪，而是变得懒惰起来，可以在<code>*</code>, <code>+</code> 加个<code>?</code>
</li>
</ul>
<div class="sourceCode" id="cb685"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">x</span> <span class="op"><-</span> <span class="st">"Roman numerals: MDCCCLXXXVIII"</span></span>
<span></span>
<span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_view.html">str_view</a></span><span class="op">(</span><span class="va">x</span>, <span class="st">"CLX+"</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [1] │ Roman numerals: MDCC<CLXXX>VIII</code></pre>
<div class="sourceCode" id="cb687"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_view.html">str_view</a></span><span class="op">(</span><span class="va">x</span>, <span class="st">"CLX+?"</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [1] │ Roman numerals: MDCC<CLX>XXVIII</code></pre>
<p>小结一下呢</p>
<div class="inline-figure"><img src="images/regex_repeat.jpg" width="75%"></div>
</div>
<div id="分组与回溯引用" class="section level3" number="15.4.5">
<h3>
<span class="header-section-number">15.4.5</span> 分组与回溯引用<a class="anchor" aria-label="anchor" href="#%E5%88%86%E7%BB%84%E4%B8%8E%E5%9B%9E%E6%BA%AF%E5%BC%95%E7%94%A8"><i class="fas fa-link"></i></a>
</h3>
<div class="sourceCode" id="cb689"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">ft</span> <span class="op"><-</span> <span class="va">fruit</span> <span class="op"><a href="https://magrittr.tidyverse.org/reference/pipe.html">%>%</a></span> <span class="fu"><a href="https://rdrr.io/r/utils/head.html">head</a></span><span class="op">(</span><span class="fl">10</span><span class="op">)</span></span>
<span><span class="va">ft</span></span></code></pre></div>
<pre><code>## [1] "apple" "apricot" "avocado" "banana" "bell pepper"
## [6] "bilberry" "blackberry" "blackcurrant" "blood orange" "blueberry"</code></pre>
<p>我们想看看这些单词里，有哪些字母是重复两次的，比如<code>aa</code>, <code>pp</code>. 如果用上面学的方法</p>
<div class="sourceCode" id="cb691"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_view.html">str_view</a></span><span class="op">(</span><span class="va">ft</span>, <span class="st">".{2}"</span>, match <span class="op">=</span> <span class="cn">TRUE</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [1] │ <ap><pl>e
## [2] │ <ap><ri><co>t
## [3] │ <av><oc><ad>o
## [4] │ <ba><na><na>
## [5] │ <be><ll>< p><ep><pe>r
## [6] │ <bi><lb><er><ry>
## [7] │ <bl><ac><kb><er><ry>
## [8] │ <bl><ac><kc><ur><ra><nt>
## [9] │ <bl><oo><d ><or><an><ge>
## [10] │ <bl><ue><be><rr>y</code></pre>
<p>发现不是和我们的预想不一样呢。</p>
<p>所以需要用到新技术 <strong>分组与回溯引用</strong>，</p>
<div class="sourceCode" id="cb693"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_view.html">str_view</a></span><span class="op">(</span><span class="va">ft</span>, <span class="st">"(.)\\1"</span>, match <span class="op">=</span> <span class="cn">TRUE</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [1] │ a<pp>le
## [5] │ be<ll> pe<pp>er
## [6] │ bilbe<rr>y
## [7] │ blackbe<rr>y
## [8] │ blackcu<rr>ant
## [9] │ bl<oo>d orange
## [10] │ bluebe<rr>y</code></pre>
<ul>
<li>
<code>.</code> 是匹配任何字符</li>
<li>
<code>(.)</code> 将匹配项括起来，它就用了一个名字，叫<code>\\1</code>； 如果有两个括号，就叫<code>\\1</code>和<code>\\2</code>
</li>
<li>
<code>\\1</code> 表示回溯引用，表示引用<code>\\1</code>对于的<code>(.)</code>
</li>
</ul>
<p>所以<code>(.)\\1</code>的意思就是，匹配到了字符，后面还希望有个<strong>同样的字符</strong></p>
<p>如果是匹配<code>abab</code>, <code>wcwc</code></p>
<div class="sourceCode" id="cb695"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_view.html">str_view</a></span><span class="op">(</span><span class="va">ft</span>, <span class="st">"(..)\\1"</span>, match <span class="op">=</span> <span class="cn">TRUE</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [4] │ b<anan>a</code></pre>
<p>如果是匹配<code>abba</code>, <code>wccw</code>呢？</p>
<div class="sourceCode" id="cb697"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_view.html">str_view</a></span><span class="op">(</span><span class="va">ft</span>, <span class="st">"(.)(.)\\2\\1"</span>, match <span class="op">=</span> <span class="cn">TRUE</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [5] │ bell p<eppe>r</code></pre>
<p>是不是很神奇？</p>
</div>
<div id="大小写敏感" class="section level3" number="15.4.6">
<h3>
<span class="header-section-number">15.4.6</span> 大小写敏感<a class="anchor" aria-label="anchor" href="#%E5%A4%A7%E5%B0%8F%E5%86%99%E6%95%8F%E6%84%9F"><i class="fas fa-link"></i></a>
</h3>
<p>希望找出线上平台是google和meet的记录，显然Google和google是一个意思，都应该被筛选出</p>
<div class="sourceCode" id="cb699"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">df</span> <span class="op"><-</span> <span class="fu">tibble</span><span class="fu">::</span><span class="fu"><a href="https://tibble.tidyverse.org/reference/tribble.html">tribble</a></span><span class="op">(</span></span>
<span> <span class="op">~</span><span class="va">tch_id</span>, <span class="op">~</span><span class="va">online_platform</span>,</span>
<span> <span class="fl">105</span>, <span class="st">"Google"</span>,</span>
<span> <span class="fl">106</span>, <span class="st">"meet"</span>,</span>
<span> <span class="fl">107</span>, <span class="st">"Zoom"</span>,</span>
<span> <span class="fl">108</span>, <span class="st">"zoom"</span>,</span>
<span> <span class="fl">109</span>, <span class="st">"Google Meet"</span>,</span>
<span> <span class="fl">112</span>, <span class="st">"Microsoft Teams"</span>,</span>
<span> <span class="fl">113</span>, <span class="cn">NA</span></span>
<span> <span class="op">)</span></span>
<span><span class="va">df</span></span></code></pre></div>
<pre><code>## # A tibble: 7 × 2
## tch_id online_platform
## <dbl> <chr>
## 1 105 Google
## 2 106 meet
## 3 107 Zoom
## 4 108 zoom
## 5 109 Google Meet
## 6 112 Microsoft Teams
## 7 113 <NA></code></pre>
<p>方法1，使用<code><a href="https://stringr.tidyverse.org/reference/modifiers.html">stringr::regex()</a></code></p>
<div class="sourceCode" id="cb701"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">df</span> <span class="op"><a href="https://magrittr.tidyverse.org/reference/pipe.html">%>%</a></span></span>
<span> <span class="fu"><a href="https://dplyr.tidyverse.org/reference/filter.html">filter</a></span><span class="op">(</span></span>
<span> <span class="fu"><a href="https://stringr.tidyverse.org/reference/str_detect.html">str_detect</a></span><span class="op">(</span><span class="va">online_platform</span>, <span class="fu"><a href="https://stringr.tidyverse.org/reference/modifiers.html">regex</a></span><span class="op">(</span><span class="st">"google|meet"</span>, ignore_case <span class="op">=</span> <span class="cn">TRUE</span><span class="op">)</span><span class="op">)</span></span>
<span> <span class="op">)</span></span></code></pre></div>
<pre><code>## # A tibble: 3 × 2
## tch_id online_platform
## <dbl> <chr>
## 1 105 Google
## 2 106 meet
## 3 109 Google Meet</code></pre>
<p>方法2，使用<code>(?i)</code></p>
<div class="sourceCode" id="cb703"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">df</span> <span class="op"><a href="https://magrittr.tidyverse.org/reference/pipe.html">%>%</a></span></span>
<span> <span class="fu"><a href="https://dplyr.tidyverse.org/reference/filter.html">filter</a></span><span class="op">(</span></span>
<span> <span class="fu"><a href="https://stringr.tidyverse.org/reference/str_detect.html">str_detect</a></span><span class="op">(</span><span class="va">online_platform</span>, <span class="st">"(?i)google|meet"</span><span class="op">)</span></span>
<span> <span class="op">)</span></span></code></pre></div>
<pre><code>## # A tibble: 3 × 2
## tch_id online_platform
## <dbl> <chr>
## 1 105 Google
## 2 106 meet
## 3 109 Google Meet</code></pre>
</div>
</div>
<div id="解决实际问题" class="section level2" number="15.5">
<h2>
<span class="header-section-number">15.5</span> 解决实际问题<a class="anchor" aria-label="anchor" href="#%E8%A7%A3%E5%86%B3%E5%AE%9E%E9%99%85%E9%97%AE%E9%A2%98"><i class="fas fa-link"></i></a>
</h2>
<div id="确定一个字符向量是否匹配一种模式" class="section level3" number="15.5.1">
<h3>
<span class="header-section-number">15.5.1</span> 确定一个字符向量是否匹配一种模式<a class="anchor" aria-label="anchor" href="#%E7%A1%AE%E5%AE%9A%E4%B8%80%E4%B8%AA%E5%AD%97%E7%AC%A6%E5%90%91%E9%87%8F%E6%98%AF%E5%90%A6%E5%8C%B9%E9%85%8D%E4%B8%80%E7%A7%8D%E6%A8%A1%E5%BC%8F"><i class="fas fa-link"></i></a>
</h3>
<p>实际问题中，想判断是否匹配？可以用到<code><a href="https://stringr.tidyverse.org/reference/str_detect.html">str_detect()</a></code>函数</p>
<div class="sourceCode" id="cb705"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">x</span> <span class="op"><-</span> <span class="fu"><a href="https://rdrr.io/r/base/c.html">c</a></span><span class="op">(</span><span class="st">"apple"</span>, <span class="st">"banana"</span>, <span class="st">"pear"</span><span class="op">)</span></span>
<span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_detect.html">str_detect</a></span><span class="op">(</span><span class="va">x</span>, <span class="st">"e"</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [1] TRUE FALSE TRUE</code></pre>
<p>数据框中也是一样</p>
<pre><code>## # A tibble: 3 × 1
## x
## <chr>
## 1 apple
## 2 banana
## 3 pear</code></pre>
<div class="sourceCode" id="cb708"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">d</span> <span class="op"><a href="https://magrittr.tidyverse.org/reference/pipe.html">%>%</a></span> <span class="fu"><a href="https://dplyr.tidyverse.org/reference/mutate.html">mutate</a></span><span class="op">(</span>has_e <span class="op">=</span> <span class="fu"><a href="https://stringr.tidyverse.org/reference/str_detect.html">str_detect</a></span><span class="op">(</span><span class="va">x</span>, <span class="st">"e"</span><span class="op">)</span><span class="op">)</span></span></code></pre></div>
<pre><code>## # A tibble: 3 × 2
## x has_e
## <chr> <lgl>
## 1 apple TRUE
## 2 banana FALSE
## 3 pear TRUE</code></pre>
<p>用于筛选也很方便</p>
<div class="sourceCode" id="cb710"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">d</span> <span class="op"><a href="https://magrittr.tidyverse.org/reference/pipe.html">%>%</a></span> <span class="fu">dplyr</span><span class="fu">::</span><span class="fu"><a href="https://dplyr.tidyverse.org/reference/filter.html">filter</a></span><span class="op">(</span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_detect.html">str_detect</a></span><span class="op">(</span><span class="va">x</span>, <span class="st">"e"</span><span class="op">)</span><span class="op">)</span></span></code></pre></div>
<pre><code>## # A tibble: 2 × 1
## x
## <chr>
## 1 apple
## 2 pear</code></pre>
<p><code><a href="https://stringr.tidyverse.org/reference/stringr-data.html">stringr::words</a></code>包含了牛津字典里常用单词</p>
<div class="sourceCode" id="cb712"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="fu">stringr</span><span class="fu">::</span><span class="va"><a href="https://stringr.tidyverse.org/reference/stringr-data.html">words</a></span> <span class="op"><a href="https://magrittr.tidyverse.org/reference/pipe.html">%>%</a></span> <span class="fu"><a href="https://rdrr.io/r/utils/head.html">head</a></span><span class="op">(</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [1] "a" "able" "about" "absolute" "accept" "account"</code></pre>
<p>我们统计下以<code>t</code>开头的单词，有多少个？</p>
<div class="sourceCode" id="cb714"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="co"># How many common words start with t?</span></span>
<span><span class="fu"><a href="https://rdrr.io/r/base/sum.html">sum</a></span><span class="op">(</span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_detect.html">str_detect</a></span><span class="op">(</span><span class="va">words</span>, <span class="st">"^t"</span><span class="op">)</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [1] 65</code></pre>
<p>我们又一次看到了<strong>强制转换</strong>.</p>
<p>以元音结尾的单词，占比多少？</p>
<div class="sourceCode" id="cb716"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="co"># proportion of common words end with a vowel?</span></span>
<span><span class="fu"><a href="https://rdrr.io/r/base/mean.html">mean</a></span><span class="op">(</span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_detect.html">str_detect</a></span><span class="op">(</span><span class="va">words</span>, <span class="st">"[aeiou]$"</span><span class="op">)</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [1] 0.2765306</code></pre>
<p>放在数据框里看看, 看看以<code>x</code>结尾的单词是哪些？</p>
<div class="sourceCode" id="cb718"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="fu"><a href="https://tibble.tidyverse.org/reference/tibble.html">tibble</a></span><span class="op">(</span></span>
<span> word <span class="op">=</span> <span class="va">words</span></span>
<span><span class="op">)</span> <span class="op"><a href="https://magrittr.tidyverse.org/reference/pipe.html">%>%</a></span></span>
<span> <span class="fu">dplyr</span><span class="fu">::</span><span class="fu"><a href="https://dplyr.tidyverse.org/reference/filter.html">filter</a></span><span class="op">(</span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_detect.html">str_detect</a></span><span class="op">(</span><span class="va">word</span>, <span class="st">"x$"</span><span class="op">)</span><span class="op">)</span></span></code></pre></div>
<pre><code>## # A tibble: 4 × 1
## word
## <chr>
## 1 box
## 2 sex
## 3 six
## 4 tax</code></pre>
<p><code><a href="https://stringr.tidyverse.org/reference/str_detect.html">str_detect()</a></code> 有一个功能类似的函数<code><a href="https://stringr.tidyverse.org/reference/str_count.html">str_count()</a></code>，区别在于，后者不是简单地返回是或否，而是返回字符串中匹配的数量</p>
<div class="sourceCode" id="cb720"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">x</span> <span class="op"><-</span> <span class="fu"><a href="https://rdrr.io/r/base/c.html">c</a></span><span class="op">(</span><span class="st">"apple"</span>, <span class="st">"banana"</span>, <span class="st">"pear"</span><span class="op">)</span></span>
<span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_count.html">str_count</a></span><span class="op">(</span><span class="va">x</span>, <span class="st">"a"</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [1] 1 3 1</code></pre>
<div class="sourceCode" id="cb722"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="fu"><a href="https://tibble.tidyverse.org/reference/tibble.html">tibble</a></span><span class="op">(</span></span>
<span> word <span class="op">=</span> <span class="va">words</span></span>
<span><span class="op">)</span> <span class="op"><a href="https://magrittr.tidyverse.org/reference/pipe.html">%>%</a></span></span>
<span> <span class="fu"><a href="https://dplyr.tidyverse.org/reference/mutate.html">mutate</a></span><span class="op">(</span></span>
<span> vowels <span class="op">=</span> <span class="fu"><a href="https://stringr.tidyverse.org/reference/str_count.html">str_count</a></span><span class="op">(</span><span class="va">word</span>, <span class="st">"[aeiou]"</span><span class="op">)</span>,</span>
<span> consonants <span class="op">=</span> <span class="fu"><a href="https://stringr.tidyverse.org/reference/str_count.html">str_count</a></span><span class="op">(</span><span class="va">word</span>, <span class="st">"[^aeiou]"</span><span class="op">)</span></span>
<span> <span class="op">)</span></span></code></pre></div>
<pre><code>## # A tibble: 980 × 3
## word vowels consonants
## <chr> <int> <int>
## 1 a 1 0
## 2 able 2 2
## 3 about 3 2
## 4 absolute 4 4
## 5 accept 2 4
## 6 account 3 4
## 7 achieve 4 3
## 8 across 2 4
## 9 act 1 2
## 10 active 3 3
## # ℹ 970 more rows</code></pre>
</div>
<div id="确定匹配的位置" class="section level3" number="15.5.2">
<h3>
<span class="header-section-number">15.5.2</span> 确定匹配的位置<a class="anchor" aria-label="anchor" href="#%E7%A1%AE%E5%AE%9A%E5%8C%B9%E9%85%8D%E7%9A%84%E4%BD%8D%E7%BD%AE"><i class="fas fa-link"></i></a>
</h3>
<p>大家放心，正则表达式不会重叠匹配。比如用<code>"aba"</code>去匹配<code>"abababa"</code>，肉眼感觉是三次，但正则表达式告诉我们是两次，因为不会重叠匹配</p>
<div class="sourceCode" id="cb724"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_count.html">str_count</a></span><span class="op">(</span><span class="st">"abababa"</span>, <span class="st">"aba"</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [1] 2</code></pre>
<div class="sourceCode" id="cb726"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_view.html">str_view_all</a></span><span class="op">(</span><span class="st">"abababa"</span>, <span class="st">"aba"</span><span class="op">)</span></span></code></pre></div>
<pre><code>## Warning: `str_view()` was deprecated in stringr 1.5.0.
## ℹ Please use `str_view_all()` instead.
## This warning is displayed once every 8 hours.
## Call `lifecycle::last_lifecycle_warnings()` to see where this warning was
## generated.</code></pre>
<pre><code>## [1] │ <aba>b<aba></code></pre>
<p>这里插播一个正则表达式”，它用于匹配单词字符与非单词字符（比如逗号、空格、句点）之间的位置。比如这里返回字符串中<code>s</code>的个数</p>
<div class="sourceCode" id="cb729"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="fu"><a href="https://rdrr.io/r/base/c.html">c</a></span><span class="op">(</span><span class="st">"she sells seashells"</span><span class="op">)</span> <span class="op"><a href="https://magrittr.tidyverse.org/reference/pipe.html">%>%</a></span> <span class="fu"><a href="https://stringr.tidyverse.org/reference/str_count.html">str_count</a></span><span class="op">(</span>pattern <span class="op">=</span> <span class="st">"s"</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [1] 6</code></pre>
<p>这里的<code>s</code>后面必须跟一个非字符的符号，比如逗号、空格、句点等，因此是2个</p>
<div class="sourceCode" id="cb731"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="fu"><a href="https://rdrr.io/r/base/c.html">c</a></span><span class="op">(</span><span class="st">"she sells seashells"</span><span class="op">)</span> <span class="op"><a href="https://magrittr.tidyverse.org/reference/pipe.html">%>%</a></span> <span class="fu"><a href="https://stringr.tidyverse.org/reference/str_count.html">str_count</a></span><span class="op">(</span>pattern <span class="op">=</span> <span class="st">"s\\b"</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [1] 2</code></pre>
</div>
<div id="提取匹配的内容" class="section level3" number="15.5.3">
<h3>
<span class="header-section-number">15.5.3</span> 提取匹配的内容<a class="anchor" aria-label="anchor" href="#%E6%8F%90%E5%8F%96%E5%8C%B9%E9%85%8D%E7%9A%84%E5%86%85%E5%AE%B9"><i class="fas fa-link"></i></a>
</h3>
<div class="sourceCode" id="cb733"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">colours</span> <span class="op"><-</span> <span class="fu"><a href="https://rdrr.io/r/base/c.html">c</a></span><span class="op">(</span></span>
<span> <span class="st">"red"</span>, <span class="st">"orange"</span>, <span class="st">"yellow"</span>,</span>
<span> <span class="st">"green"</span>, <span class="st">"blue"</span>, <span class="st">"purple"</span></span>
<span><span class="op">)</span></span>
<span><span class="va">colour_match</span> <span class="op"><-</span> <span class="fu"><a href="https://stringr.tidyverse.org/reference/str_c.html">str_c</a></span><span class="op">(</span><span class="va">colours</span>, collapse <span class="op">=</span> <span class="st">"|"</span><span class="op">)</span></span>
<span><span class="va">colour_match</span></span></code></pre></div>
<pre><code>## [1] "red|orange|yellow|green|blue|purple"</code></pre>
<p>colour_match 这里是一个字符串，放在pattern参数位置上也是正则表达式了,</p>
<p>这里注意以下两者的区别</p>
<div class="sourceCode" id="cb735"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_view.html">str_view</a></span><span class="op">(</span><span class="st">"abcd"</span>, <span class="st">"ab|cd"</span><span class="op">)</span></span>
<span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_view.html">str_view</a></span><span class="op">(</span><span class="st">"abc"</span>, <span class="st">"a[bc]d"</span><span class="op">)</span></span></code></pre></div>
<div class="sourceCode" id="cb736"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">more</span> <span class="op"><-</span> <span class="st">"It is hard to erase blue or red ink."</span></span>
<span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_extract.html">str_extract</a></span><span class="op">(</span><span class="va">more</span>, pattern <span class="op">=</span> <span class="va">colour_match</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [1] "blue"</code></pre>
<div class="sourceCode" id="cb738"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_extract.html">str_extract_all</a></span><span class="op">(</span><span class="va">more</span>, pattern <span class="op">=</span> <span class="va">colour_match</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [[1]]
## [1] "blue" "red"</code></pre>
<div class="sourceCode" id="cb740"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">more</span> <span class="op"><-</span> <span class="va">sentences</span><span class="op">[</span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_count.html">str_count</a></span><span class="op">(</span><span class="va">sentences</span>, <span class="va">colour_match</span><span class="op">)</span> <span class="op">></span> <span class="fl">1</span><span class="op">]</span></span>
<span><span class="va">more</span></span></code></pre></div>
<pre><code>## [1] "It is hard to erase blue or red ink."
## [2] "The green light in the brown box flickered."
## [3] "The sky in the west is tinged with orange red."</code></pre>
<p>取出sentences中，含有有两种和两种颜色以上的句子。不过，不喜欢这种写法，看着费劲，还是用tidyverse的方法</p>
<div class="sourceCode" id="cb742"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="fu"><a href="https://tibble.tidyverse.org/reference/tibble.html">tibble</a></span><span class="op">(</span>sentence <span class="op">=</span> <span class="va">sentences</span><span class="op">)</span> <span class="op"><a href="https://magrittr.tidyverse.org/reference/pipe.html">%>%</a></span></span>
<span> <span class="fu"><a href="https://dplyr.tidyverse.org/reference/filter.html">filter</a></span><span class="op">(</span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_count.html">str_count</a></span><span class="op">(</span><span class="va">sentences</span>, <span class="va">colour_match</span><span class="op">)</span> <span class="op">></span> <span class="fl">1</span><span class="op">)</span></span></code></pre></div>
<pre><code>## # A tibble: 3 × 1
## sentence
## <chr>
## 1 It is hard to erase blue or red ink.
## 2 The green light in the brown box flickered.
## 3 The sky in the west is tinged with orange red.</code></pre>
<p><code><a href="https://stringr.tidyverse.org/reference/str_extract.html">str_extract()</a></code>提取匹配, 谁先匹配就提取谁</p>
<div class="sourceCode" id="cb744"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="fu"><a href="https://tibble.tidyverse.org/reference/tibble.html">tibble</a></span><span class="op">(</span>x <span class="op">=</span> <span class="va">more</span><span class="op">)</span> <span class="op"><a href="https://magrittr.tidyverse.org/reference/pipe.html">%>%</a></span></span>
<span> <span class="fu"><a href="https://dplyr.tidyverse.org/reference/mutate.html">mutate</a></span><span class="op">(</span>color <span class="op">=</span> <span class="fu"><a href="https://stringr.tidyverse.org/reference/str_extract.html">str_extract</a></span><span class="op">(</span><span class="va">x</span>, <span class="va">colour_match</span><span class="op">)</span><span class="op">)</span></span></code></pre></div>
<pre><code>## # A tibble: 3 × 2
## x color
## <chr> <chr>
## 1 It is hard to erase blue or red ink. blue
## 2 The green light in the brown box flickered. green
## 3 The sky in the west is tinged with orange red. orange</code></pre>
<p><code><a href="https://stringr.tidyverse.org/reference/str_extract.html">str_extract_all()</a></code>提取全部匹配项</p>
<div class="sourceCode" id="cb746"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="fu"><a href="https://tibble.tidyverse.org/reference/tibble.html">tibble</a></span><span class="op">(</span>x <span class="op">=</span> <span class="va">more</span><span class="op">)</span> <span class="op"><a href="https://magrittr.tidyverse.org/reference/pipe.html">%>%</a></span></span>
<span> <span class="fu"><a href="https://dplyr.tidyverse.org/reference/mutate.html">mutate</a></span><span class="op">(</span>color <span class="op">=</span> <span class="fu"><a href="https://stringr.tidyverse.org/reference/str_extract.html">str_extract_all</a></span><span class="op">(</span><span class="va">x</span>, <span class="va">colour_match</span><span class="op">)</span><span class="op">)</span></span></code></pre></div>
<pre><code>## # A tibble: 3 × 2
## x color
## <chr> <list>
## 1 It is hard to erase blue or red ink. <chr [2]>
## 2 The green light in the brown box flickered. <chr [2]>
## 3 The sky in the west is tinged with orange red. <chr [2]></code></pre>
<div class="sourceCode" id="cb748"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="fu"><a href="https://tibble.tidyverse.org/reference/tibble.html">tibble</a></span><span class="op">(</span>x <span class="op">=</span> <span class="va">more</span><span class="op">)</span> <span class="op"><a href="https://magrittr.tidyverse.org/reference/pipe.html">%>%</a></span></span>
<span> <span class="fu"><a href="https://dplyr.tidyverse.org/reference/mutate.html">mutate</a></span><span class="op">(</span>color <span class="op">=</span> <span class="fu"><a href="https://stringr.tidyverse.org/reference/str_extract.html">str_extract_all</a></span><span class="op">(</span><span class="va">x</span>, <span class="va">colour_match</span><span class="op">)</span><span class="op">)</span> <span class="op"><a href="https://magrittr.tidyverse.org/reference/pipe.html">%>%</a></span></span>
<span> <span class="fu"><a href="https://tidyr.tidyverse.org/reference/unnest.html">unnest</a></span><span class="op">(</span><span class="va">color</span><span class="op">)</span></span></code></pre></div>
<pre><code>## # A tibble: 6 × 2
## x color
## <chr> <chr>
## 1 It is hard to erase blue or red ink. blue
## 2 It is hard to erase blue or red ink. red
## 3 The green light in the brown box flickered. green
## 4 The green light in the brown box flickered. red
## 5 The sky in the west is tinged with orange red. orange
## 6 The sky in the west is tinged with orange red. red</code></pre>
</div>
<div id="替换匹配内容" class="section level3" number="15.5.4">
<h3>
<span class="header-section-number">15.5.4</span> 替换匹配内容<a class="anchor" aria-label="anchor" href="#%E6%9B%BF%E6%8D%A2%E5%8C%B9%E9%85%8D%E5%86%85%E5%AE%B9"><i class="fas fa-link"></i></a>
</h3>
<p>只替换匹配的第一项</p>
<div class="sourceCode" id="cb750"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">x</span> <span class="op"><-</span> <span class="fu"><a href="https://rdrr.io/r/base/c.html">c</a></span><span class="op">(</span><span class="st">"apple"</span>, <span class="st">"pear"</span>, <span class="st">"banana"</span><span class="op">)</span></span>
<span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_replace.html">str_replace</a></span><span class="op">(</span><span class="va">x</span>, <span class="st">"[aeiou]"</span>, <span class="st">"-"</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [1] "-pple" "p-ar" "b-nana"</code></pre>
<p>替换全部匹配项</p>
<div class="sourceCode" id="cb752"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_replace.html">str_replace_all</a></span><span class="op">(</span><span class="va">x</span>, <span class="st">"[aeiou]"</span>, <span class="st">"-"</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [1] "-ppl-" "p--r" "b-n-n-"</code></pre>
</div>
<div id="拆分字符串" class="section level3" number="15.5.5">
<h3>
<span class="header-section-number">15.5.5</span> 拆分字符串<a class="anchor" aria-label="anchor" href="#%E6%8B%86%E5%88%86%E5%AD%97%E7%AC%A6%E4%B8%B2"><i class="fas fa-link"></i></a>
</h3>
<p>这个和<code><a href="https://stringr.tidyverse.org/reference/str_c.html">str_c()</a></code>是相反的操作</p>
<div class="sourceCode" id="cb754"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">lines</span> <span class="op"><-</span> <span class="st">"I love my country"</span></span>
<span><span class="va">lines</span></span></code></pre></div>
<pre><code>## [1] "I love my country"</code></pre>
<div class="sourceCode" id="cb756"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_split.html">str_split</a></span><span class="op">(</span><span class="va">lines</span>, <span class="st">" "</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [[1]]
## [1] "I" "love" "my" "country"</code></pre>
<div class="sourceCode" id="cb758"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">fields</span> <span class="op"><-</span> <span class="fu"><a href="https://rdrr.io/r/base/c.html">c</a></span><span class="op">(</span><span class="st">"Name: Hadley"</span>, <span class="st">"Country: NZ"</span>, <span class="st">"Age: 35"</span><span class="op">)</span></span>
<span><span class="va">fields</span> <span class="op"><a href="https://magrittr.tidyverse.org/reference/pipe.html">%>%</a></span> <span class="fu"><a href="https://stringr.tidyverse.org/reference/str_split.html">str_split</a></span><span class="op">(</span><span class="st">": "</span>, n <span class="op">=</span> <span class="fl">2</span>, simplify <span class="op">=</span> <span class="cn">TRUE</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [,1] [,2]
## [1,] "Name" "Hadley"
## [2,] "Country" "NZ"
## [3,] "Age" "35"</code></pre>
</div>
</div>
<div id="进阶部分" class="section level2" number="15.6">
<h2>
<span class="header-section-number">15.6</span> 进阶部分<a class="anchor" aria-label="anchor" href="#%E8%BF%9B%E9%98%B6%E9%83%A8%E5%88%86"><i class="fas fa-link"></i></a>
</h2>
<p>带有条件的匹配</p>
<div id="look-ahead" class="section level3" number="15.6.1">
<h3>
<span class="header-section-number">15.6.1</span> look ahead<a class="anchor" aria-label="anchor" href="#look-ahead"><i class="fas fa-link"></i></a>
</h3>
<p>想匹配Windows，同时希望Windows右侧是<code>"95", "98", "NT", "2000"</code>中的一个</p>
<div class="sourceCode" id="cb760"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">win</span> <span class="op"><-</span> <span class="fu"><a href="https://rdrr.io/r/base/c.html">c</a></span><span class="op">(</span><span class="st">"Windows2000"</span>, <span class="st">"Windows"</span>, <span class="st">"Windows3.1"</span><span class="op">)</span></span>
<span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_view.html">str_view</a></span><span class="op">(</span><span class="va">win</span>, <span class="st">"Windows(?=95|98|NT|2000)"</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [1] │ <Windows>2000</code></pre>
<div class="sourceCode" id="cb762"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">win</span> <span class="op"><-</span> <span class="fu"><a href="https://rdrr.io/r/base/c.html">c</a></span><span class="op">(</span><span class="st">"Windows2000"</span>, <span class="st">"Windows"</span>, <span class="st">"Windows3.1"</span><span class="op">)</span></span>
<span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_view.html">str_view</a></span><span class="op">(</span><span class="va">win</span>, <span class="st">"Windows(?!95|98|NT|2000)"</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [2] │ <Windows>
## [3] │ <Windows>3.1</code></pre>
<p>Windows后面的 <code>()</code> 是匹配条件，事实上，有四种情形：</p>
<ul>
<li>
<code>(?=pattern)</code> 要求此位置的后面必须匹配表达式pattern</li>
<li>
<code>(?!pattern)</code> 要求此位置的后面不能匹配表达式pattern</li>
<li>
<code>(?<=pattern)</code> 要求此位置的前面必须匹配表达式pattern</li>
<li>
<code>(?<!pattern)</code> 要求此位置的前面不能匹配表达式pattern</li>
</ul>
<div class="danger">
<p>
注意：对于正则表达式引擎来说，它是从文本头部向尾部（从左到右）开始解析的，因此对于文本尾部方向，称为“前”，因为这个时候，正则引擎还没走到那块；而对文本头部方向，则称为“后”，因为正则引擎已经走过了那一块地方。
</p>
</div>
</div>
<div id="look-behind" class="section level3" number="15.6.2">
<h3>
<span class="header-section-number">15.6.2</span> look behind<a class="anchor" aria-label="anchor" href="#look-behind"><i class="fas fa-link"></i></a>
</h3>
<div class="sourceCode" id="cb764"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">win</span> <span class="op"><-</span> <span class="fu"><a href="https://rdrr.io/r/base/c.html">c</a></span><span class="op">(</span><span class="st">"2000Windows"</span>, <span class="st">"Windows"</span>, <span class="st">"3.1Windows"</span><span class="op">)</span></span>
<span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_view.html">str_view</a></span><span class="op">(</span><span class="va">win</span>, <span class="st">"(?<=95|98|NT|2000)Windows"</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [1] │ 2000<Windows></code></pre>
<div class="sourceCode" id="cb766"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">win</span> <span class="op"><-</span> <span class="fu"><a href="https://rdrr.io/r/base/c.html">c</a></span><span class="op">(</span><span class="st">"2000Windows"</span>, <span class="st">"Windows"</span>, <span class="st">"3.1Windows"</span><span class="op">)</span></span>
<span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_view.html">str_view</a></span><span class="op">(</span><span class="va">win</span>, <span class="st">"(?<!95|98|NT|2000)Windows"</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [2] │ <Windows>
## [3] │ 3.1<Windows></code></pre>
</div>
</div>
<div id="案例分析" class="section level2" number="15.7">
<h2>
<span class="header-section-number">15.7</span> 案例分析<a class="anchor" aria-label="anchor" href="#%E6%A1%88%E4%BE%8B%E5%88%86%E6%9E%90"><i class="fas fa-link"></i></a>
</h2>
<div id="案例1" class="section level3" number="15.7.1">
<h3>
<span class="header-section-number">15.7.1</span> 案例1<a class="anchor" aria-label="anchor" href="#%E6%A1%88%E4%BE%8B1"><i class="fas fa-link"></i></a>
</h3>
<p>我们希望能提取第二列中的数值，构成新的一列</p>
<div class="sourceCode" id="cb768"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">dt</span> <span class="op"><-</span> <span class="fu"><a href="https://tibble.tidyverse.org/reference/tibble.html">tibble</a></span><span class="op">(</span></span>
<span> x <span class="op">=</span> <span class="fl">1</span><span class="op">:</span><span class="fl">4</span>,</span>
<span> y <span class="op">=</span> <span class="fu"><a href="https://rdrr.io/r/base/c.html">c</a></span><span class="op">(</span><span class="st">"wk 3"</span>, <span class="st">"week-1"</span>, <span class="st">"7"</span>, <span class="st">"w#9"</span><span class="op">)</span></span>
<span><span class="op">)</span></span>
<span><span class="va">dt</span></span></code></pre></div>
<pre><code>## # A tibble: 4 × 2
## x y
## <int> <chr>
## 1 1 wk 3
## 2 2 week-1
## 3 3 7
## 4 4 w#9</code></pre>
<div class="sourceCode" id="cb770"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">dt</span> <span class="op"><a href="https://magrittr.tidyverse.org/reference/pipe.html">%>%</a></span></span>
<span> <span class="fu"><a href="https://dplyr.tidyverse.org/reference/mutate.html">mutate</a></span><span class="op">(</span></span>
<span> z <span class="op">=</span> <span class="fu"><a href="https://stringr.tidyverse.org/reference/str_extract.html">str_extract</a></span><span class="op">(</span><span class="va">y</span>, <span class="st">"[0-9]"</span><span class="op">)</span></span>
<span> <span class="op">)</span></span></code></pre></div>
<pre><code>## # A tibble: 4 × 3
## x y z
## <int> <chr> <chr>
## 1 1 wk 3 3
## 2 2 week-1 1
## 3 3 7 7
## 4 4 w#9 9</code></pre>
</div>
<div id="案例2" class="section level3" number="15.7.2">
<h3>
<span class="header-section-number">15.7.2</span> 案例2<a class="anchor" aria-label="anchor" href="#%E6%A1%88%E4%BE%8B2"><i class="fas fa-link"></i></a>
</h3>
<p>提取第二列中的大写字母</p>
<div class="sourceCode" id="cb772"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">df</span> <span class="op"><-</span> <span class="fu"><a href="https://rdrr.io/r/base/data.frame.html">data.frame</a></span><span class="op">(</span></span>
<span> x <span class="op">=</span> <span class="fu"><a href="https://rdrr.io/r/base/seq.html">seq_along</a></span><span class="op">(</span><span class="fl">1</span><span class="op">:</span><span class="fl">7</span><span class="op">)</span>,</span>
<span> y <span class="op">=</span> <span class="fu"><a href="https://rdrr.io/r/base/c.html">c</a></span><span class="op">(</span><span class="st">"2016123456"</span>, <span class="st">"20150513"</span>, <span class="st">"AB2016123456"</span>, <span class="st">"J2017000987"</span>, <span class="st">"B2017000987C"</span>, <span class="st">"aksdf"</span>, <span class="st">"2014"</span><span class="op">)</span></span>
<span><span class="op">)</span></span>
<span><span class="va">df</span></span></code></pre></div>
<pre><code>## x y
## 1 1 2016123456
## 2 2 20150513
## 3 3 AB2016123456
## 4 4 J2017000987
## 5 5 B2017000987C
## 6 6 aksdf
## 7 7 2014</code></pre>
<div class="sourceCode" id="cb774"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">df</span> <span class="op"><a href="https://magrittr.tidyverse.org/reference/pipe.html">%>%</a></span></span>
<span> <span class="fu"><a href="https://dplyr.tidyverse.org/reference/mutate.html">mutate</a></span><span class="op">(</span></span>
<span> item <span class="op">=</span> <span class="fu"><a href="https://stringr.tidyverse.org/reference/str_extract.html">str_extract_all</a></span><span class="op">(</span><span class="va">y</span>, <span class="st">"[A-Z]"</span><span class="op">)</span></span>
<span> <span class="op">)</span> <span class="op"><a href="https://magrittr.tidyverse.org/reference/pipe.html">%>%</a></span></span>
<span> <span class="fu">tidyr</span><span class="fu">::</span><span class="fu"><a href="https://tidyr.tidyverse.org/reference/unnest.html">unnest</a></span><span class="op">(</span><span class="va">item</span><span class="op">)</span></span></code></pre></div>
<pre><code>## # A tibble: 5 × 3
## x y item
## <int> <chr> <chr>
## 1 3 AB2016123456 A
## 2 3 AB2016123456 B
## 3 4 J2017000987 J
## 4 5 B2017000987C B
## 5 5 B2017000987C C</code></pre>
</div>
<div id="案例3" class="section level3" number="15.7.3">
<h3>
<span class="header-section-number">15.7.3</span> 案例3<a class="anchor" aria-label="anchor" href="#%E6%A1%88%E4%BE%8B3"><i class="fas fa-link"></i></a>
</h3>
<p>要求：中英文分开</p>
<div class="sourceCode" id="cb776"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">tb</span> <span class="op"><a href="https://magrittr.tidyverse.org/reference/pipe.html">%>%</a></span></span>
<span> <span class="fu">tidyr</span><span class="fu">::</span><span class="fu"><a href="https://tidyr.tidyverse.org/reference/extract.html">extract</a></span><span class="op">(</span></span>
<span> <span class="co"># x, c("en", "cn"), "([:alpha:]+)([^:alpha:]+)",</span></span>
<span> <span class="va">x</span>, <span class="fu"><a href="https://rdrr.io/r/base/c.html">c</a></span><span class="op">(</span><span class="st">"en"</span>, <span class="st">"cn"</span><span class="op">)</span>, <span class="st">"([a-zA-Z]+)([^a-zA-Z]+)"</span>,</span>
<span> remove <span class="op">=</span> <span class="cn">FALSE</span></span>
<span> <span class="op">)</span></span></code></pre></div>
<pre><code>## # A tibble: 3 × 3
## x en cn
## <chr> <chr> <chr>
## 1 I我 I 我
## 2 love爱 love 爱
## 3 you你 you 你</code></pre>
</div>
<div id="案例4" class="section level3" number="15.7.4">
<h3>
<span class="header-section-number">15.7.4</span> 案例4<a class="anchor" aria-label="anchor" href="#%E6%A1%88%E4%BE%8B4"><i class="fas fa-link"></i></a>
</h3>
<p>要求：提取起始数字</p>
<div class="sourceCode" id="cb778"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">df</span> <span class="op"><-</span> <span class="fu"><a href="https://tibble.tidyverse.org/reference/tibble.html">tibble</a></span><span class="op">(</span>x <span class="op">=</span> <span class="fu"><a href="https://rdrr.io/r/base/c.html">c</a></span><span class="op">(</span><span class="st">"1-12week"</span>, <span class="st">"1-10week"</span>, <span class="st">"5-12week"</span><span class="op">)</span><span class="op">)</span></span>
<span><span class="va">df</span></span></code></pre></div>
<pre><code>## # A tibble: 3 × 1
## x
## <chr>
## 1 1-12week
## 2 1-10week
## 3 5-12week</code></pre>
<div class="sourceCode" id="cb780"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">df</span> <span class="op"><a href="https://magrittr.tidyverse.org/reference/pipe.html">%>%</a></span> <span class="fu"><a href="https://tidyr.tidyverse.org/reference/extract.html">extract</a></span><span class="op">(</span></span>
<span> <span class="va">x</span>,</span>
<span> <span class="co"># c("start", "end", "cn"), "([:digit:]+)-([:digit:]+)([^:alpha:]+)",</span></span>
<span> <span class="fu"><a href="https://rdrr.io/r/base/c.html">c</a></span><span class="op">(</span><span class="st">"start"</span>, <span class="st">"end"</span>, <span class="st">"cn"</span><span class="op">)</span>, <span class="st">"(\\d+)-(\\d+)(\\D+)"</span>,</span>
<span> remove <span class="op">=</span> <span class="cn">FALSE</span></span>
<span><span class="op">)</span></span></code></pre></div>
<pre><code>## # A tibble: 3 × 4
## x start end cn
## <chr> <chr> <chr> <chr>
## 1 1-12week 1 12 week
## 2 1-10week 1 10 week
## 3 5-12week 5 12 week</code></pre>
</div>
<div id="案例5" class="section level3" number="15.7.5">
<h3>
<span class="header-section-number">15.7.5</span> 案例5<a class="anchor" aria-label="anchor" href="#%E6%A1%88%E4%BE%8B5"><i class="fas fa-link"></i></a>
</h3>
<p>要求：提取大写字母后的数字</p>
<div class="sourceCode" id="cb782"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">df</span> <span class="op"><-</span> <span class="fu"><a href="https://tibble.tidyverse.org/reference/tibble.html">tibble</a></span><span class="op">(</span></span>
<span> x <span class="op">=</span> <span class="fu"><a href="https://rdrr.io/r/base/c.html">c</a></span><span class="op">(</span><span class="st">"12W34"</span>, <span class="st">"AB2C46"</span>, <span class="st">"B217C"</span>, <span class="st">"akTs6df"</span>, <span class="st">"21WD4"</span><span class="op">)</span></span>
<span><span class="op">)</span></span></code></pre></div>
<div class="sourceCode" id="cb783"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">df</span> <span class="op"><a href="https://magrittr.tidyverse.org/reference/pipe.html">%>%</a></span></span>
<span> <span class="fu"><a href="https://dplyr.tidyverse.org/reference/mutate.html">mutate</a></span><span class="op">(</span>item <span class="op">=</span> <span class="fu"><a href="https://stringr.tidyverse.org/reference/str_extract.html">str_extract_all</a></span><span class="op">(</span><span class="va">x</span>, <span class="st">"(?<=[A-Z])[0-9]"</span><span class="op">)</span><span class="op">)</span> <span class="op"><a href="https://magrittr.tidyverse.org/reference/pipe.html">%>%</a></span></span>
<span> <span class="fu">tidyr</span><span class="fu">::</span><span class="fu"><a href="https://tidyr.tidyverse.org/reference/unnest.html">unnest</a></span><span class="op">(</span><span class="va">item</span><span class="op">)</span></span></code></pre></div>
<pre><code>## # A tibble: 5 × 2
## x item
## <chr> <chr>
## 1 12W34 3
## 2 AB2C46 2
## 3 AB2C46 4
## 4 B217C 2
## 5 21WD4 4</code></pre>
<p>思考题，</p>
<ul>
<li>如何提取大写字母后的连续数字，比如B217C后面的217</li>
<li>如何提取提取数字前的大写字母？</li>
<li>为什么第一个正则表达式返回结果为””</li>
</ul>
<div class="sourceCode" id="cb785"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">x</span> <span class="op"><-</span> <span class="st">"Roman numerals: MDCCCLXXXVIII"</span></span>
<span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_match.html">str_match_all</a></span><span class="op">(</span><span class="va">x</span>, <span class="st">"C?"</span><span class="op">)</span> </span></code></pre></div>
<pre><code>## [[1]]
## [,1]
## [1,] ""
## [2,] ""
## [3,] ""
## [4,] ""
## [5,] ""
## [6,] ""
## [7,] ""
## [8,] ""
## [9,] ""
## [10,] ""
## [11,] ""
## [12,] ""
## [13,] ""
## [14,] ""
## [15,] ""
## [16,] ""
## [17,] ""
## [18,] ""
## [19,] "C"
## [20,] "C"
## [21,] "C"
## [22,] ""
## [23,] ""
## [24,] ""
## [25,] ""
## [26,] ""
## [27,] ""
## [28,] ""
## [29,] ""
## [30,] ""</code></pre>
<div class="sourceCode" id="cb787"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="fu"><a href="https://stringr.tidyverse.org/reference/str_match.html">str_match_all</a></span><span class="op">(</span><span class="va">x</span>, <span class="st">"CC?"</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [[1]]
## [,1]
## [1,] "CC"
## [2,] "C"</code></pre>
<p>“?”的意思是匹配0次或者1次</p>
</div>
<div id="案例6" class="section level3" number="15.7.6">
<h3>
<span class="header-section-number">15.7.6</span> 案例6<a class="anchor" aria-label="anchor" href="#%E6%A1%88%E4%BE%8B6"><i class="fas fa-link"></i></a>
</h3>
<p>提取数字并求和</p>
<div class="sourceCode" id="cb789"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">df</span> <span class="op"><-</span> <span class="fu"><a href="https://tibble.tidyverse.org/reference/tibble.html">tibble</a></span><span class="op">(</span></span>
<span> x <span class="op">=</span> <span class="fu"><a href="https://rdrr.io/r/base/c.html">c</a></span><span class="op">(</span><span class="st">"1234"</span>, <span class="st">"B246"</span>, <span class="st">"217C"</span>, <span class="st">"2357f"</span>, <span class="st">"21WD4"</span><span class="op">)</span></span>
<span><span class="op">)</span></span>
<span><span class="va">df</span></span></code></pre></div>
<pre><code>## # A tibble: 5 × 1
## x
## <chr>
## 1 1234
## 2 B246
## 3 217C
## 4 2357f
## 5 21WD4</code></pre>
<div class="sourceCode" id="cb791"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">df</span> <span class="op"><a href="https://magrittr.tidyverse.org/reference/pipe.html">%>%</a></span></span>
<span> <span class="fu"><a href="https://dplyr.tidyverse.org/reference/mutate.html">mutate</a></span><span class="op">(</span>num <span class="op">=</span> <span class="fu"><a href="https://stringr.tidyverse.org/reference/str_match.html">str_match_all</a></span><span class="op">(</span><span class="va">x</span>, <span class="st">"\\d"</span><span class="op">)</span><span class="op">)</span> <span class="op"><a href="https://magrittr.tidyverse.org/reference/pipe.html">%>%</a></span></span>
<span> <span class="fu"><a href="https://tidyr.tidyverse.org/reference/unnest.html">unnest</a></span><span class="op">(</span><span class="va">num</span><span class="op">)</span> <span class="op"><a href="https://magrittr.tidyverse.org/reference/pipe.html">%>%</a></span></span>
<span> <span class="fu"><a href="https://dplyr.tidyverse.org/reference/mutate_all.html">mutate_at</a></span><span class="op">(</span><span class="fu"><a href="https://ggplot2.tidyverse.org/reference/vars.html">vars</a></span><span class="op">(</span><span class="va">num</span><span class="op">)</span>, <span class="va">as.numeric</span><span class="op">)</span> <span class="op"><a href="https://magrittr.tidyverse.org/reference/pipe.html">%>%</a></span></span>
<span> <span class="fu"><a href="https://dplyr.tidyverse.org/reference/group_by.html">group_by</a></span><span class="op">(</span><span class="va">x</span><span class="op">)</span> <span class="op"><a href="https://magrittr.tidyverse.org/reference/pipe.html">%>%</a></span></span>
<span> <span class="fu"><a href="https://dplyr.tidyverse.org/reference/summarise.html">summarise</a></span><span class="op">(</span>sum <span class="op">=</span> <span class="fu"><a href="https://rdrr.io/r/base/sum.html">sum</a></span><span class="op">(</span><span class="va">num</span><span class="op">)</span><span class="op">)</span></span></code></pre></div>
<pre><code>## # A tibble: 5 × 2
## x sum
## <chr> <dbl>
## 1 1234 10
## 2 217C 10
## 3 21WD4 7
## 4 2357f 17
## 5 B246 12</code></pre>
</div>
<div id="案例7" class="section level3" number="15.7.7">
<h3>
<span class="header-section-number">15.7.7</span> 案例7<a class="anchor" aria-label="anchor" href="#%E6%A1%88%E4%BE%8B7"><i class="fas fa-link"></i></a>
</h3>