package com.excellence.splitsentence;

import java.net.UnknownHostException;

import java.util.ArrayList;

import java.util.Arrays;

import java.util.Collections;

import java.util.List;

import org.jblas.ComplexDoubleMatrix;

import org.jblas.ComplexFloatMatrix;

import org.jblas.DoubleMatrix;

import org.jblas.Eigen;

import org.jblas.FloatMatrix;

import com.mongodb.BasicDBList;

import com.mongodb.DB;

import com.mongodb.DBCollection;

import com.mongodb.DBCursor;

import com.mongodb.MongoClient;

import com.mongodb.MongoCredential;

import com.mongodb.ServerAddress;

public class PCA {

     /**

      * Reduce matrix dimension     减少矩阵维度

      * @param source         源矩阵

      * @param dimension       目标维度

      * @return Target matrix     返回目标矩阵

      */ 

    public static FloatMatrix dimensionReduction(FloatMatrix source, int dimension) {

        //C=X*X^t/m     矩阵*矩阵^异或/列数

        FloatMatrix covMatrix = source.mmul(source.transpose()).div(source.columns);

        ComplexFloatMatrix eigVal = Eigen.eigenvalues(covMatrix);

        ComplexFloatMatrix[] eigVectorsVal = Eigen.eigenvectors(covMatrix);

        ComplexFloatMatrix eigVectors = eigVectorsVal[0];

        //通过特征值将符号向量从大到小排序

        List<PCABean> beans = new ArrayList<PCA.PCABean>();

        for (int i = 0; i < eigVectors.columns; i++) {

            beans.add(new PCABean(eigVal.get(i).real(), eigVectors.getColumn(i)));

        }

        Collections.sort(beans);

        FloatMatrix newVec = new FloatMatrix(dimension, beans.get(0).vector.rows);

        for (int i = 0; i < dimension; i++) {

            ComplexFloatMatrix dm = beans.get(i).vector;

            FloatMatrix real = dm.getReal();

            newVec.putRow(i, real);

        }

        return newVec.mmul(source);

    }

    static class PCABean implements Comparable<PCABean> {

        float eigenValue;

        ComplexFloatMatrix vector;

        public PCABean(Float eigenValue, ComplexFloatMatrix vector) {

            super();

            this.eigenValue = eigenValue;

            this.vector = vector;

        }

        @Override

        public int compareTo(PCABean o) {

            return Float.compare(o.eigenValue, eigenValue);

        }

        @Override

        public String toString() {

            return "PCABean [eigenValue=" + eigenValue + ", vector=" + vector + "]";

        }

    }

}

如何调用？

float[] vector = docvector.getElementArray();
FloatMatrix d = new FloatMatrix(vector);

FloatMatrix result = PCA.dimensionReduction(d, 10);