public double logDensity()

in commons-statistics-distribution/src/main/java/org/apache/commons/statistics/distribution/BetaDistribution.java [126:159]

• 24 lines of code
• 8 McCabe index (conditional complexity)

    public double logDensity(double x) {
        if (x < 0 || x > 1) {
            return Double.NEGATIVE_INFINITY;
        } else if (x == 0) {
            if (alpha < 1) {
                // Distribution is not valid when x=0, alpha<1
                // due to a divide by zero error.
                // Do not raise an exception and return the limit.
                return Double.POSITIVE_INFINITY;
            }
            // Special case of cancellation: x^(a-1) (1-x)^(b-1) / B(a, b) = 1 / B(a, b)
            if (alpha == 1) {
                return -logBeta;
            }
            return Double.NEGATIVE_INFINITY;
        } else if (x == 1) {
            if (beta < 1) {
                // Distribution is not valid when x=1, beta<1
                // due to a divide by zero error.
                // Do not raise an exception and return the limit.
                return Double.POSITIVE_INFINITY;
            }
            // Special case of cancellation: x^(a-1) (1-x)^(b-1) / B(a, b) = 1 / B(a, b)
            if (beta == 1) {
                return -logBeta;
            }
            return Double.NEGATIVE_INFINITY;
        }

        // Log computation
        final double logX = Math.log(x);
        final double log1mX = Math.log1p(-x);
        return (alpha - 1) * logX + (beta - 1) * log1mX - logBeta;
    }