Weibull

Weibull distribution constructor.

Usage

var Weibull = require( '@stdlib/math/base/dists/weibull/ctor' );

Weibull( [k, lambda] )

Returns a Weibull distribution object.

var weibull = new Weibull();

var mode = weibull.mode;
// returns 0.0

By default, k = 1.0 and lambda = 1.0. To create a distribution having a different k (shape parameter) and lambda (scale parameter), provide parameter values.

var weibull = new Weibull( 2.0, 4.0 );

var mode = weibull.mode;
// returns ~2.828

weibull

A Weibull distribution object has the following properties and methods...

Writable Properties

weibull.k

Shape parameter of the distribution. k must be a positive number.

var weibull = new Weibull();

var k = weibull.k;
// returns 1.0

weibull.k = 3.0;

k = weibull.k;
// returns 3.0

weibull.lambda

Scale parameter of the distribution. lambda must be a positive number.

var weibull = new Weibull( 2.0, 4.0 );

var lambda = weibull.lambda;
// returns 4.0

weibull.lambda = 3.0;

lambda = weibull.lambda;
// returns 3.0

Computed Properties

Weibull.prototype.entropy

Returns the differential entropy.

var weibull = new Weibull( 4.0, 12.0 );

var entropy = weibull.entropy;
// returns ~2.531

Weibull.prototype.kurtosis

Returns the excess kurtosis.

var weibull = new Weibull( 4.0, 12.0 );

var kurtosis = weibull.kurtosis;
// returns ~-0.252

Weibull.prototype.mean

Returns the expected value.

var weibull = new Weibull( 4.0, 12.0 );

var mu = weibull.mean;
// returns ~10.877

Weibull.prototype.mode

Returns the mode.

var weibull = new Weibull( 4.0, 12.0 );

var mode = weibull.mode;
// returns ~11.167

Weibull.prototype.skewness

Returns the skewness.

var weibull = new Weibull( 4.0, 12.0 );

var skewness = weibull.skewness;
// returns ~-0.087

Weibull.prototype.stdev

Returns the standard deviation.

var weibull = new Weibull( 4.0, 12.0 );

var s = weibull.stdev;
// returns ~3.051

Weibull.prototype.variance

Returns the variance.

var weibull = new Weibull( 4.0, 12.0 );

var s2 = weibull.variance;
// returns ~9.311

Methods

Weibull.prototype.cdf( x )

Evaluates the cumulative distribution function (CDF).

var weibull = new Weibull( 2.0, 4.0 );

var y = weibull.cdf( 0.5 );
// returns ~0.016

Weibull.prototype.logcdf( x )

Evaluates the natural logarithm of the cumulative distribution function (logCDF).

var weibull = new Weibull( 2.0, 4.0 );

var y = weibull.logcdf( 0.8 );
// returns ~-3.239

Weibull.prototype.logpdf( x )

Evaluates the natural logarithm of the probability density function (PDF).

var weibull = new Weibull( 2.0, 4.0 );

var y = weibull.logpdf( 0.8 );
// returns ~-2.343

Weibull.prototype.mgf( t )

Evaluates the moment-generating function (MGF).

var weibull = new Weibull( 2.0, 4.0 );

var y = weibull.mgf( 0.5 );
// returns ~9.878

Weibull.prototype.pdf( x )

Evaluates the probability density function (PDF).

var weibull = new Weibull( 2.0, 4.0 );

var y = weibull.pdf( 0.8 );
// returns ~0.096

Weibull.prototype.quantile( p )

Evaluates the quantile function at probability p.

var weibull = new Weibull( 2.0, 4.0 );

var y = weibull.quantile( 0.5 );
// returns ~3.33

y = quantile( 1.9 );
// returns NaN

Examples

var Weibull = require( '@stdlib/math/base/dists/weibull/ctor' );

var weibull = new Weibull( 2.0, 4.0 );

var mu = weibull.mean;
// returns ~3.545

var mode = weibull.mode;
// returns ~2.828

var s2 = weibull.variance;
// returns ~3.434

var y = weibull.cdf( 0.8 );
// returns ~0.039