KNN算法--投票猜黨派

KNN分類方法可以理解為投票法。把訓(xùn)練數(shù)據(jù)集當(dāng)做選民，K值當(dāng)做這些選民所擁有的選票?，F(xiàn)在從這些這些選民中推選出來(lái)的K位投票人，推選的標(biāo)準(zhǔn) 是和候選黨派（假設(shè)這個(gè)黨派名稱對(duì)選民是保密的，實(shí)際中可以理解為測(cè)試數(shù)據(jù)）的政策主張（數(shù)據(jù)特征）相近程度。而這些投票人自己本身又有自己所屬的黨派，他們當(dāng)然把選票投給自己的黨派。得票最多的黨派獲勝，這時(shí)候我們就有較大的把握認(rèn)為得票多的黨派就是候選人的黨派名稱。

一個(gè)手勢(shì)識(shí)別的KNN應(yīng)用實(shí)例

    /**
     * @param trainingData2
     * @param vec2
     * @return the distance of two vectors
     */
     public double EulerDistance(Double[] trainingData2,double[] vec2){
        double tdis = 0.0;
        double ans = 0.0;
        double dis = 0.0;
        for(int i = 0;i<vecLen;i++){
            dis = (trainingData2[i] - vec2[i]);
            tdis += dis * dis;
        }
        ans = Math.sqrt(tdis);
        return ans;
    }
     
     
    /**
     * the Entrance method of this class,from one to six marks the name
     * of all the gestures,and this method returns the name of gesture 
     * that most matching.
     * Using KNN algorithm
     * @return name of gesture
     */
    class Node implements Comparable<Node>{
        public double dis;
        public int gid;
        public Node(int _gid,double _dis) {
            this.gid = _gid;
            this.dis = _dis;
        }
        @Override
        public int compareTo(Node o) {
            if(this.dis > o.dis) return 1;
            else if(this.dis < o.dis) return -1;
            else return 0;
        }
    }
    public int GestureResult(double[] inData,int k){
        ArrayList<Node> nodes = new ArrayList<>();
        int[] vote = {0,0,0,0,0,0};
        for(int i = 0;i<6;i++){
            for(int j = 0;j<60;j++){
                nodes.add(new Node(i,EulerDistance(trainingData[i][j], inData)));
            }
        }
        Collections.sort(nodes);
        for(int i = 0;i<k;i++){
            vote[nodes.get(i).gid]++;
        }
        int ans_index = 0;
        int most = -1;
        for(int i = 0;i<6;i++){
            if(vote[i] > most){
                ans_index = i;
                most = vote[i];
            }
        }
       return GestrueName[ans_index];
    }