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Probability Density Function
Exponential distribution probability density function (PDF).
The probability density function (PDF) for an exponential random variable is
where λ
is the rate parameter.
Usage
var pdf = require( '@stdlib/stats/base/dists/exponential/pdf' );
pdf( x, lambda )
Evaluates the probability density function (PDF) for an exponential distribution with rate parameter lambda
.
var y = pdf( 2.0, 0.3 );
// returns ~0.165
y = pdf( 2.0, 1.0 );
// returns ~0.135
If provided NaN
as any argument, the function returns NaN
.
var y = pdf( NaN, 0.0 );
// returns NaN
y = pdf( 0.0, NaN );
// returns NaN
If provided lambda < 0
, the function returns NaN
.
var y = pdf( 2.0, -1.0 );
// returns NaN
pdf.factory( lambda )
Partially apply lambda
to create a reusable function
for evaluating the PDF.
var mypdf = pdf.factory( 0.1 );
var y = mypdf( 8.0 );
// returns ~0.045
y = mypdf( 5.0 );
// returns ~0.06
Examples
var randu = require( '@stdlib/random/base/randu' );
var pdf = require( '@stdlib/stats/base/dists/exponential/pdf' );
var lambda;
var x;
var y;
var i;
for ( i = 0; i < 10; i++ ) {
x = randu() * 10.0;
lambda = randu() * 10.0;
y = pdf( x, lambda );
console.log( 'x: %d, λ: %d, f(x;λ): %d', x, lambda, y );
}