stdlib-js
<summary>
About stdlib...
</summary>
We believe in a future in which the web is a preferred environment for numerical computation. To help realize this future, we've built stdlib. stdlib is a standard library, with an emphasis on numerical and scientific computation, written in JavaScript (and C) for execution in browsers and in Node.js.
The library is fully decomposable, being architected in such a way that you can swap out and mix and match APIs and functionality to cater to your exact preferences and use cases.
When you use stdlib, you can be absolutely certain that you are using the most thorough, rigorous, well-written, studied, documented, tested, measured, and high-quality code out there.
To join us in bringing numerical computing to the web, get started by checking us out on GitHub, and please consider financially supporting stdlib. We greatly appreciate your continued support!
Cumulative Distribution Function
[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url]
[Chi-squared][chisquare-distribution] distribution [cumulative distribution function][cdf].
k is the degrees of freedom and P is the lower regularized incomplete gamma function.
bash
npm install @stdlib/stats-base-dists-chisquare-cdf
javascript
var cdf = require( '@stdlib/stats-base-dists-chisquare-cdf' );
#### cdf( x, k )
Evaluates the [cumulative distribution function][cdf] (CDF) for a [chi-squared][chisquare-distribution] distribution with degrees of freedom k.
javascript
var y = cdf( 2.0, 1.0 );
// returns ~0.843
y = cdf( 2.0, 3.0 );
// returns ~0.428
y = cdf( 1.0, 0.5 );
// returns ~0.846
y = cdf( -1.0, 2.0 );
// returns 0.0
y = cdf( -Infinity, 4.0 );
// returns 0.0
y = cdf( +Infinity, 4.0 );
// returns 1.0
If provided NaN as any argument, the function returns NaN.
javascript
var y = cdf( NaN, 1.0 );
// returns NaN
y = cdf( 0.0, NaN );
// returns NaN
If provided k < 0, the function returns NaN.
javascript
var y = cdf( 2.0, -2.0 );
// returns NaN
If provided k = 0, the function evaluates the [CDF][cdf] of a [degenerate distribution][degenerate-distribution] centered at 0.
javascript
var y = cdf( 2.0, 0.0 );
// returns 1.0
y = cdf( -2.0, 0.0 );
// returns 0.0
y = cdf( 0.0, 0.0 );
// returns 1.0
#### cdf.factory( k )
Returns a function for evaluating the [cumulative distribution function][cdf] for a [chi-squared][chisquare-distribution] distribution with degrees of freedom k.
javascript
var mycdf = cdf.factory( 3.0 );
var y = mycdf( 6.0 );
// returns ~0.888
y = mycdf( 1.5 );
// returns ~0.318
javascript
var randu = require( '@stdlib/random-base-randu' );
var round = require( '@stdlib/math-base-special-round' );
var cdf = require( '@stdlib/stats-base-dists-chisquare-cdf' );
var k;
var x;
var y;
var i;
for ( i = 0; i < 20; i++ ) {
x = randu() * 10.0;
k = round( randu()*5.0 );
y = cdf( x, k );
console.log( 'x: %d, k: %d, F(x;k): %d', x.toFixed( 4 ), k.toFixed( 4 ), y.toFixed( 4 ) );
}
