Example usage for org.apache.commons.math3.util MathArrays checkPositive

Introduction

In this page you can find the example usage for org.apache.commons.math3.util MathArrays checkPositive.

Prototype

public static void checkPositive(final double[] in) throws NotStrictlyPositiveException 

Source Link

Document

Check that all entries of the input array are strictly positive.

Usage

From source file:hivemall.utils.math.StatsUtils.java

/**
 * @param observed means non-negative vector
 * @param expected means positive vector
 * @return chi2 value// w  w w. j  av a 2  s. c  o m
 */
public static double chiSquare(@Nonnull final double[] observed, @Nonnull final double[] expected) {
    if (observed.length < 2) {
        throw new DimensionMismatchException(observed.length, 2);
    }
    if (expected.length != observed.length) {
        throw new DimensionMismatchException(observed.length, expected.length);
    }
    MathArrays.checkPositive(expected);
    for (double d : observed) {
        if (d < 0.d) {
            throw new NotPositiveException(d);
        }
    }

    double sumObserved = 0.d;
    double sumExpected = 0.d;
    for (int i = 0; i < observed.length; i++) {
        sumObserved += observed[i];
        sumExpected += expected[i];
    }
    double ratio = 1.d;
    boolean rescale = false;
    if (FastMath.abs(sumObserved - sumExpected) > 10e-6) {
        ratio = sumObserved / sumExpected;
        rescale = true;
    }
    double sumSq = 0.d;
    for (int i = 0; i < observed.length; i++) {
        if (rescale) {
            final double dev = observed[i] - ratio * expected[i];
            sumSq += dev * dev / (ratio * expected[i]);
        } else {
            final double dev = observed[i] - expected[i];
            sumSq += dev * dev / expected[i];
        }
    }
    return sumSq;
}

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