Returns chi-square probability for even numbers number. - Java java.lang

Java examples for java.lang:Math Number

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Description

Returns chi-square probability for even numbers number.

Demo Code


//package com.java2s;

public class Main {
    /**//from w w w  . j av a 2  s . c  o m
     * Returns chi-square probability for even numbers number.
     */
    public static double chiSquareProbEven(int number, double value) {
        double result = 0;
        for (int idx = 0; idx <= (number / 2 - 1); idx++) {
            result += (1 / gammaFunction(idx + 1))
                    * Math.pow(value / 2, idx);
        }
        return Math.exp(-value / 2) * result;
    }

    /**
     * Returns gamma value for a double in.
     */
    public static double gammaFunction(double in) {
        if (in == 1.0) {
            return 1.0;
        }
        if (in == 0.5) {
            return Math.sqrt(Math.PI);
        }
        return (in - 1) * gammaFunction(in - 1);
    }
}

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