@stdlib/stats
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Standard library statistical functions.
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{{alias}}( x, λ )
Evaluates the natural logarithm of the probability density function (PDF)
for an exponential distribution with rate parameter `λ` at a value `x`.
If provided `NaN` as any argument, the function returns `NaN`.
If provided a negative value for `λ`, the function returns `NaN`.
Parameters
----------
x: number
Input value.
λ: number
Rate parameter.
Returns
-------
out: number
Evaluated logPDF.
Examples
--------
> var y = {{alias}}( 0.3, 4.0 )
~0.186
> y = {{alias}}( 2.0, 0.7 )
~-1.757
> y = {{alias}}( -1.0, 0.5 )
-Infinity
> y = {{alias}}( 0, NaN )
NaN
> y = {{alias}}( NaN, 2.0 )
NaN
// Negative rate:
> y = {{alias}}( 2.0, -1.0 )
NaN
{{alias}}.factory( λ )
Returns a function for evaluating the natural logarithm of the probability
density function (PDF) for an exponential distribution with rate parameter
`λ`.
Parameters
----------
λ: number
Rate parameter.
Returns
-------
logpdf: Function
Logarithm of probability density function (PDF).
Examples
--------
> var mylogpdf = {{alias}}.factory( 0.5 );
> var y = mylogpdf( 3.0 )
~-2.193
See Also
--------