@stdlib/stats
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Standard library statistical functions.
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{{alias}}( x, α, β )
Evaluates the natural logarithm of the probability density function (PDF)
for an inverse gamma distribution with shape parameter `α` and scale
parameter `β` at a value `x`.
If `α <= 0` or `β <= 0`, the function returns `NaN`.
If provided `NaN` as any argument, the function returns `NaN`.
Parameters
----------
x: number
Input value.
α: number
Shape parameter.
β: number
Scale parameter.
Returns
-------
out: number
Evaluated logPDF.
Examples
--------
> var y = {{alias}}( 2.0, 0.5, 1.0 )
~-2.112
> y = {{alias}}( 0.2, 1.0, 1.0 )
~-1.781
> y = {{alias}}( -1.0, 4.0, 2.0 )
-Infinity
> y = {{alias}}( NaN, 1.0, 1.0 )
NaN
> y = {{alias}}( 0.0, NaN, 1.0 )
NaN
> y = {{alias}}( 0.0, 1.0, NaN )
NaN
// Negative shape parameter:
> y = {{alias}}( 2.0, -1.0, 1.0 )
NaN
// Negative scale parameter:
> y = {{alias}}( 2.0, 1.0, -1.0 )
NaN
{{alias}}.factory( α, β )
Returns a function for evaluating the natural logarithm of the probability
density function (PDF) for an inverse gamma distribution with shape
parameter `α` and scale parameter `β`.
Parameters
----------
α: number
Shape parameter.
β: number
Scale parameter.
Returns
-------
logpdf: Function
Logarithm of probability density function (PDF).
Examples
--------
> var mylogPDF = {{alias}}.factory( 6.0, 7.0 );
> var y = mylogPDF( 2.0 )
~-1.464
See Also
--------