贝塔函数与伽马函数的关系 详细推导过程见LDA漫游指南 java的org.apache.commons.math3.special.Gamma封装了Gamma函数可以直接使用 本文首先计算出B(3.9,2.9)与B(3.9,5.3)的100个散点，然后绘制出Beta分布图像

import java.io.BufferedWriter;import java.io.FileWriter;import java.io.IOException;import org.apache.commons.math3.special.Gamma;public class betadistr {                        public static double Gammafun(double alpha){                    return Gamma.gamma(alpha);                         }         public static double Bfunction(double alpha,double beta) {            double totgamm = Gammafun(alpha+beta);            double addgamm = Gammafun(alpha)*Gammafun(beta);            return addgamm/totgamm;        }         public static void valued() throws IOException {                        BufferedWriter writer = new BufferedWriter(new FileWriter(filename));                        int K=2;            double[][] m=new double[K][100];                        double b[][]= new double[2][2];            b[0][0]= 3.9;            b[0][1]= 2.9;            b[1][0]= 3.9;            b[1][1]= 5.3;                                                                                       for (int i = 0; i < K; i++) {                                for (int x = 0; x < 100; x++) {                        double y = (double)x/100;                                    double f=Math.pow(y,b[i][0]-1)*Math.pow(1-y, b[i][1]-1);                                                double z=Bfunction(b[i][0],b[i][1]);                        m[i][x]=f/z;                        writer.write(m[i][x] + "\t");                        System.out.println(m[i][x]);                   }                writer.write("\n");               }                                                      writer.close();                                                  }                                           public static void main(String[] args) throws IOException {            valued();                     }    }