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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="active" 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>
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<li><a class="" href="tidyverse-readr.html"><span class="header-section-number">10</span> 读取数据</a></li>
<li><a class="" href="tidyverse-dplyr.html"><span class="header-section-number">11</span> 数据处理</a></li>
<li><a class="" href="tidyverse-dplyr-apply.html"><span class="header-section-number">12</span> dplyr进阶</a></li>
<li><a class="" href="tidyverse-tidyr.html"><span class="header-section-number">13</span> 数据规整1</a></li>
<li><a class="" href="tidyverse-tidyr2.html"><span class="header-section-number">14</span> 数据规整2</a></li>
<li><a class="" 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-theme.html"><span class="header-section-number">21</span> ggplot2之主题设置</a></li>
<li><a class="" href="tidyverse-ggplot2-guides.html"><span class="header-section-number">22</span> ggplot2之图例系统</a></li>
<li><a class="" href="tidyverse-ggplot2-customize.html"><span class="header-section-number">23</span> ggplot2之扩展内容</a></li>
<li><a class="" href="tidyverse-ggplot2-stat-layer.html"><span class="header-section-number">24</span> ggplot2之统计图层</a></li>
<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>
<li class="book-part">可重复性文档Rmarkdown以及练习</li>
<li><a class="" href="tidyverse-rmarkdown.html"><span class="header-section-number">32</span> 可重复性文档</a></li>
<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>
<li><a class="" href="GO-KEGG.html"><span class="header-section-number">34</span> GO/KEGG功能富集分析</a></li>
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</header><main class="col-sm-12 col-md-9 col-lg-7" id="content"><div id="baseR-objects" class="section level1" number="3">
<h1>
<span class="header-section-number">第 3 章</span> 对象<a class="anchor" aria-label="anchor" href="#baseR-objects"><i class="fas fa-link"></i></a>
</h1>
<div id="对象的创建与使用" class="section level2" number="3.1">
<h2>
<span class="header-section-number">3.1</span> 对象的创建与使用<a class="anchor" aria-label="anchor" href="#%E5%AF%B9%E8%B1%A1%E7%9A%84%E5%88%9B%E5%BB%BA%E4%B8%8E%E4%BD%BF%E7%94%A8"><i class="fas fa-link"></i></a>
</h2>
<p>创建一个R对象，首先确定一个名称，然后使用赋值操作符 <code><-</code>，将数据赋值给它。</p>
<div class="inline-figure"><img src="images/rsyntax1.png" width="65%"></div>
<p>我们给这个盒子取名 <code>x</code>，然后把5这个数放入<strong>盒子</strong>，用计算机语言描述就是，给变量 x 赋值为 5，在命令行中可以这样写 <code>x <- 5</code> ，然后回车.</p>
<div class="sourceCode" id="cb9"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">x</span> <span class="op"><-</span> <span class="fl">5</span></span></code></pre></div>
<div class="rmdnote">
<p>快速产生赋值符号<code><-</code>，在Rstudio中同时按下</p>
<ul>
<li>
<code>alt</code> 和 <code>-</code>（windows系统）</li>
<li>
<code>option</code> 和 <code>-</code>（苹果系统）</li>
</ul>
<div class="inline-figure"><img src="images/keyboard/keyboard_assignment.png" width="100%"></div>
</div>
<p>当键入 <code>x</code> 然后回车，就打印出 <code>x</code> 的值。当然也可以使用命令<code>print(x)</code>，结果一样。</p>
<div class="sourceCode" id="cb10"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">x</span></span></code></pre></div>
<pre><code>## [1] 5</code></pre>
</div>
<div id="变量命名规则" class="section level2" number="3.2">
<h2>
<span class="header-section-number">3.2</span> 变量命名规则<a class="anchor" aria-label="anchor" href="#%E5%8F%98%E9%87%8F%E5%91%BD%E5%90%8D%E8%A7%84%E5%88%99"><i class="fas fa-link"></i></a>
</h2>
<p>R变量名必须以字母、数字、下划线<code>_</code>和句点<code>.</code>组成。但是，变量名的第一个字符不能为数字或者特殊符号，比如 <code>+</code>, <code>-</code>, <code>*</code>, <code>/</code>, <code>^</code>, <code>!</code>, <code>@</code>, <code>&</code>, 或者下划线<code>_</code>。变量名的第一个字符如果是句点<code>.</code>，那么句点后面不能紧跟数字。变量名是区分大小写的，<code>y</code>和<code>Y</code>是两个不同的变量名。在中文环境下，汉字也可以作为变量名的合法字符使用，但不推荐使用。</p>
<ul>
<li>大小写敏感</li>
<li>不能有空格，可以用下划线代替空格，比如，<code>my_age <- 30</code>
</li>
<li>开头不能是数字和一些特殊符号</li>
</ul>
<p>为了让代码可读性更强，我们希望变量名能更清晰描述所赋值的对象，比如我们测量了男生的身高，并把测量结果存储为对象，那么这里有三种方案：</p>
<ul>
<li>一般的变量名</li>
</ul>
<div class="sourceCode" id="cb12"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">x</span> <span class="op"><-</span> <span class="fl">175</span></span></code></pre></div>
<ul>
<li>不错变量名</li>
</ul>
<div class="sourceCode" id="cb13"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">height</span> <span class="op"><-</span> <span class="fl">175</span></span></code></pre></div>
<ul>
<li>更佳的变量名</li>
</ul>
<div class="sourceCode" id="cb14"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">boy_height_cm</span> <span class="op"><-</span> <span class="fl">175</span></span></code></pre></div>
<p>很显然，第三种方案是最佳的，它清晰告诉我们男生的身高是175，测量单位是cm</p>
</div>
<div id="对象属性" class="section level2" number="3.3">
<h2>
<span class="header-section-number">3.3</span> 对象属性<a class="anchor" aria-label="anchor" href="#%E5%AF%B9%E8%B1%A1%E5%B1%9E%E6%80%A7"><i class="fas fa-link"></i></a>
</h2>
<p>所有R对象都有其属性，其中最重要的两个属性是<strong>类型</strong>和<strong>长度</strong>，我们可以用以下两个命令查看对象的类型和长度。</p>
<div class="sourceCode" id="cb15"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="fu"><a href="https://rdrr.io/r/base/typeof.html">typeof</a></span><span class="op">(</span><span class="va">x</span><span class="op">)</span> </span></code></pre></div>
<pre><code>## [1] "double"</code></pre>
<div class="sourceCode" id="cb17"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="fu"><a href="https://rdrr.io/r/base/length.html">length</a></span><span class="op">(</span><span class="va">x</span><span class="op">)</span></span></code></pre></div>
<pre><code>## [1] 1</code></pre>
</div>
</div>
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<div class="prev"><a href="baseR-install.html"><span class="header-section-number">2</span> 安装与环境配置</a></div>
<div class="next"><a href="baseR-vectors.html"><span class="header-section-number">4</span> 向量</a></div>
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<li><a class="nav-link" href="#baseR-objects"><span class="header-section-number">3</span> 对象</a></li>
<li><a class="nav-link" href="#%E5%AF%B9%E8%B1%A1%E7%9A%84%E5%88%9B%E5%BB%BA%E4%B8%8E%E4%BD%BF%E7%94%A8"><span class="header-section-number">3.1</span> 对象的创建与使用</a></li>
<li><a class="nav-link" href="#%E5%8F%98%E9%87%8F%E5%91%BD%E5%90%8D%E8%A7%84%E5%88%99"><span class="header-section-number">3.2</span> 变量命名规则</a></li>
<li><a class="nav-link" href="#%E5%AF%B9%E8%B1%A1%E5%B1%9E%E6%80%A7"><span class="header-section-number">3.3</span> 对象属性</a></li>
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