The OpenD Programming Language

gammaLPDF

mir stat distribution gamma

Computes the gamma log probability density function (LPDF).

shape values less than 1 are supported when it is a floating point type.

If shape is passed as a size_t type (or a type convertible to that), then the LPDF is calculated using the relationship with the poisson distribution (i.e. replacing the logGamma function with the logFactorial).

  1. T gammaLPDF(T x, T shape, T scale)
  2. T gammaLPDF(T x, size_t shape, T scale)
    @safe pure nothrow @nogc
    T
    gammaLPDF
    (
    T
    )
    (
    const T x
    ,
    const size_t shape
    ,
    const T scale = 1
    )
    if (
    isFloatingPoint!T
    )

Parameters

x T

value to evaluate LPDF

shape size_t

shape parameter

scale T

scale parameter

Examples

import mir.test: shouldApprox;

2.0.gammaLPDF(3.0).shouldApprox == -1.306853;
2.0.gammaLPDF(3.0, 4.0).shouldApprox == -3.965736;
// Calling with `size_t` uses log factorial function instead of log gamma,
// but produces same results
2.0.gammaLPDF(3).shouldApprox == 2.0.gammaLPDF(3.0);
2.0.gammaLPDF(3, 4.0).shouldApprox == 2.0.gammaLPDF(3.0, 4.0);

See Also

Gamma Distribution

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Source

See Implementation

mir stat distribution gamma functions
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