Computes Euclidean distance between two vectors - Java java.lang

Java examples for java.lang:Math Vector

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Description

Computes Euclidean distance between two vectors

Demo Code


//package com.java2s;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;

import java.util.Map;
import java.util.Set;

public class Main {
    /**/*from   w ww  .  j ava2s.  c o m*/
     * 
     * Computes Euclidean distance between two vectors
     * 
     * @param vector1
     * @param vector2
     * @return score
     */
    public static double computeEuclideanDistance(
            Map<String, Integer> vector1, Map<String, Integer> vector2) {
        Map<String, Integer> subtractVector = subtract(vector1, vector2);
        return Math.sqrt(dot(subtractVector, subtractVector));
    }

    /**
     * 
     * Perform a vector subtraction between two vectors
     * 
     * @param vector1
     * @param vector2
     * @return subtract
     */
    public static Map<String, Integer> subtract(
            Map<String, Integer> vector1, Map<String, Integer> vector2) {
        Map<String, Integer> subtract = new HashMap<String, Integer>();
        Set<String> vector1Vocab = vector1.keySet();
        Set<String> vector2Vocab = vector2.keySet();
        Set<String> vectorVocab = new HashSet<String>(0);
        vectorVocab.addAll(vector1Vocab);
        vectorVocab.addAll(vector2Vocab);
        Iterator<String> iter = vectorVocab.iterator();
        Integer vector1Freq;
        Integer vector2Freq;
        String word = null;
        while (iter.hasNext()) {
            word = iter.next();
            vector1Freq = new Integer(0);
            vector2Freq = new Integer(0);

            if (vector1.containsKey(word)) {
                vector1Freq = vector1.get(word);
            }
            if (vector2.containsKey(word)) {
                vector2Freq = vector2.get(word);
            }
            subtract.put(word, new Integer(vector1Freq.intValue()
                    - vector2Freq.intValue()));
        }
        return subtract;
    }

    /**
     * 
     * Perform a vector dot product between two vectors
     * 
     * @param vector1
     * @param vector2
     * @return dotproduct
     */
    public static double dot(Map<String, Integer> vector1,
            Map<String, Integer> vector2) {
        double dotproduct = 0.0;
        Set<String> vector1Vocab = vector1.keySet();
        Iterator<String> iter = vector1Vocab.iterator();
        Integer vector1Freq;
        Integer vector2Freq;
        String word = null;
        while (iter.hasNext()) {
            word = iter.next();
            vector1Freq = vector1.get(word);
            if (vector2.containsKey(word)) {
                vector2Freq = vector2.get(word);
            } else {
                continue;
            }
            dotproduct = dotproduct + (vector1Freq * vector2Freq);
        }
        return dotproduct;
    }
}

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