cosine.go

package stringosim

import (
	"strings"
)

type CosineSimilarityOptions struct {
	CaseInsensitive bool
	NGramSizes      []int
}

var DefaultCosineSimilarityOptions = CosineSimilarityOptions{
	CaseInsensitive: false,
	NGramSizes:      []int{2},
}

func Cosine(s []rune, t []rune, options ...CosineSimilarityOptions) float64 {
	if len(s) == 0 {
		if len(t) == 0 {
			return float64(0.0)
		} else {
			return float64(1.0)
		}
	} else {
		if len(t) == 0 {
			return float64(1.0)
		}
	}
	opt := DefaultCosineSimilarityOptions
	for _, option := range options {
		opt = option
		break
	}
	var sGrams, tGrams map[string]int
	if opt.CaseInsensitive {
		sGrams = GetNGram(strings.ToLower(string(s)), opt.NGramSizes)
		tGrams = GetNGram(strings.ToLower(string(t)), opt.NGramSizes)
	} else {
		sGrams = GetNGram(string(s), opt.NGramSizes)
		tGrams = GetNGram(string(t), opt.NGramSizes)
	}
	return 1.0 - float64(DotProductNGrams(sGrams, tGrams))/NormNGram(sGrams)/NormNGram(tGrams)
}