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Gamma distribution constructor.
npm install @stdlib/stats-base-dists-gamma-ctor
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var Gamma = require( '@stdlib/stats-base-dists-gamma-ctor' );
Returns a gamma distribution object.
var gamma = new Gamma();
var mode = gamma.mode;
// returns 0.0
By default, alpha = 1.0
and beta = 1.0
. To create a distribution having a different alpha
(shape parameter) and beta
(rate parameter), provide the corresponding arguments.
var gamma = new Gamma( 2.0, 4.0 );
var mu = gamma.mean;
// returns 0.5
A gamma distribution object has the following properties and methods...
Shape parameter of the distribution. alpha
must be a positive number.
var gamma = new Gamma();
var alpha = gamma.alpha;
// returns 1.0
gamma.alpha = 3.0;
alpha = gamma.alpha;
// returns 3.0
Rate parameter of the distribution. beta
must be a positive number.
var gamma = new Gamma( 2.0, 4.0 );
var b = gamma.beta;
// returns 4.0
gamma.beta = 3.0;
b = gamma.beta;
// returns 3.0
Returns the differential entropy.
var gamma = new Gamma( 4.0, 12.0 );
var entropy = gamma.entropy;
// returns ~-0.462
Returns the excess kurtosis.
var gamma = new Gamma( 4.0, 12.0 );
var kurtosis = gamma.kurtosis;
// returns 1.5
Returns the expected value.
var gamma = new Gamma( 4.0, 12.0 );
var mu = gamma.mean;
// returns ~0.333
Returns the mode.
var gamma = new Gamma( 4.0, 12.0 );
var mode = gamma.mode;
// returns 0.25
Returns the skewness.
var gamma = new Gamma( 4.0, 12.0 );
var skewness = gamma.skewness;
// returns 1.0
Returns the standard deviation.
var gamma = new Gamma( 4.0, 12.0 );
var s = gamma.stdev;
// returns ~0.167
Returns the variance.
var gamma = new Gamma( 4.0, 12.0 );
var s2 = gamma.variance;
// returns ~0.028
Evaluates the cumulative distribution function (CDF).
var gamma = new Gamma( 2.0, 4.0 );
var y = gamma.cdf( 0.5 );
// returns ~0.594
Evaluates the natural logarithm of the cumulative distribution function (CDF).
var gamma = new Gamma( 2.0, 4.0 );
var y = gamma.logcdf( 0.5 );
// returns ~-0.521
Evaluates the natural logarithm of the probability density function (PDF).
var gamma = new Gamma( 2.0, 4.0 );
var y = gamma.logpdf( 0.8 );
// returns ~-0.651
Evaluates the moment-generating function (MGF).
var gamma = new Gamma( 2.0, 4.0 );
var y = gamma.mgf( 0.5 );
// returns ~1.306
Evaluates the probability density function (PDF).
var gamma = new Gamma( 2.0, 4.0 );
var y = gamma.pdf( 0.8 );
// returns ~0.522
Evaluates the quantile function at probability p
.
var gamma = new Gamma( 2.0, 4.0 );
var y = gamma.quantile( 0.5 );
// returns ~0.42
y = gamma.quantile( 1.9 );
// returns NaN
var Gamma = require( '@stdlib/stats-base-dists-gamma-ctor' );
var gamma = new Gamma( 2.0, 4.0 );
var mu = gamma.mean;
// returns 0.5
var mode = gamma.mode;
// returns 0.25
var s2 = gamma.variance;
// returns 0.125
var y = gamma.cdf( 0.8 );
// returns ~0.829
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.
See LICENSE.
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