document distance using vector space model

docdist.go

package main

import (
	"bufio"
	"fmt"
	"math"
	"strings"
)

// document distance using vector dot product
func main() {
	// make map of words with occurances
	// use . product on these maps
	// use the angle as the basis of comparision
	str1 := "hello world cat hello hello hello world cat"
	str2 := "hello world cat hello hello world cat hello"

	wc1 := countWords(str1)
	wc2 := countWords(str2)

	var val1 float64
	var div1 float64
	var div2 float64

	for w, p1 := range wc1 {
		div1 += p1 * p1
		if p2, ok := wc2[w]; ok {
			val1 += float64(p1 * p2)
			div2 += p2 * p2
		}
	}

	val1 = val1 / (math.Sqrt(div1) * math.Sqrt(div2))

	fmt.Println(val1)
	fmt.Println(57.296, math.Acos(val1), "degrees")
}

func countWords(str string) (wordCount map[string]float64) {
	wordCount = make(map[string]float64)
	scanner := bufio.NewScanner(strings.NewReader(str))
	scanner.Split(bufio.ScanWords)
	position := 0
	for scanner.Scan() {
		wordCount[scanner.Text()] += float64(1 + position)
		position++
	}

	return wordCount
}