@stdlib/stats-base-dists-geometric-logpmf
v0.2.2
Published
Geometric distribution logarithm of probability mass function (PMF).
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Logarithm of Probability Mass Function
Geometric distribution logarithm of probability mass function (PMF).
The probability mass function (PMF) for a geometric random variable is defined as
where 0 <= p <= 1
is the success probability. The random variable X
denotes the number of failures until the first success in a sequence of independent Bernoulli trials.
Installation
npm install @stdlib/stats-base-dists-geometric-logpmf
Usage
var logpmf = require( '@stdlib/stats-base-dists-geometric-logpmf' );
logpmf( x, p )
Evaluates the logarithm of the probability mass function (PMF) of a geometric distribution with success probability 0 <= p <= 1
.
var y = logpmf( 4.0, 0.3 );
// returns ~-2.631
y = logpmf( 2.0, 0.7 );
// returns ~-2.765
y = logpmf( -1.0, 0.5 );
// returns -Infinity
If provided NaN
as any argument, the function returns NaN
.
var y = logpmf( NaN, 0.0 );
// returns NaN
y = logpmf( 0.0, NaN );
// returns NaN
If provided a success probability p
outside of the interval [0,1]
, the function returns NaN
.
var y = logpmf( 2.0, -1.0 );
// returns NaN
y = logpmf( 2.0, 1.5 );
// returns NaN
logpmf.factory( p )
Returns a function for evaluating the logarithm of the probability mass function (PMF) of a geometric distribution with success probability 0 <= p <= 1
.
var mylogpmf = logpmf.factory( 0.5 );
var y = mylogpmf( 3.0 );
// returns ~-2.773
y = mylogpmf( 1.0 );
// returns ~-1.386
Notes
- In virtually all cases, using the
logpmf
orlogcdf
functions is preferable to manually computing the logarithm of thepmf
orcdf
, respectively, since the latter is prone to overflow and underflow.
Examples
var randu = require( '@stdlib/random-base-randu' );
var round = require( '@stdlib/math-base-special-round' );
var logpmf = require( '@stdlib/stats-base-dists-geometric-logpmf' );
var p;
var x;
var y;
var i;
for ( i = 0; i < 10; i++ ) {
x = round( randu() * 5.0 );
p = randu();
y = logpmf( x, p );
console.log( 'x: %d, p: %d, ln( P( X = x; p ) ): %d', x, p.toFixed( 4 ), y.toFixed( 4 ) );
}
Notice
This package is part of stdlib, a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.
For more information on the project, filing bug reports and feature requests, and guidance on how to develop stdlib, see the main project repository.
Community
License
See LICENSE.
Copyright
Copyright © 2016-2024. The Stdlib Authors.