java实现Beta函数

<dependency>
   <groupId>org.apache.commons</groupId>
   <artifactId>commons-math3</artifactId>
   <version>3.6.1</version>
</dependency>

Gamma.gamma(double a)

public static double beta(double a, double b) {
     double beta = Gamma.gamma(a) * Gamma.gamma(b) / Gamma.gamma(a + b);
     return beta;
}

public static double betainc(double x, double a, double b) {
     return (Math.pow(x, a - 1) * Math.pow((1 - x), (b - 1))) / beta(a, b);
}