stdlib-js
<summary>
About stdlib...
</summary>
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betainc
[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url]
[Incomplete beta function][incomplete-beta-function].
bash
npm install @stdlib/math-base-special-betainc
javascript
var betainc = require( '@stdlib/math-base-special-betainc' );
#### betainc( x, a, b[, regularized[, upper]] )
By default, evaluates the regularized lower [incomplete beta function][incomplete-beta-function] for inputs x, a > 0 and b > 0. The fourth and fifth parameters of the function can be used to specify whether instead to evaluate the non-regularized and/or upper incomplete beta functions, respectively.
javascript
var y = betainc( 0.5, 2.0, 2.0 );
// returns 0.5
y = betainc( 0.5, 2.0, 2.0, false );
// returns ~0.083
y = betainc( 0.2, 1.0, 2.0 );
// returns 0.36
y = betainc( 0.2, 1.0, 2.0, true, true );
// returns 0.64
If provided NaN as any argument, the function returns NaN.
javascript
var y = betainc( NaN, 1.0, 1.0 );
// returns NaN
y = betainc( 0.8, NaN, 1.0 );
// returns NaN
y = betainc( 0.8, 1.0, NaN );
// returns NaN
If provided a x outside the interval [0,1], the function returns NaN.
javascript
var y = betainc( 1.5, 1.0, 1.0 );
// returns NaN
y = betainc( -0.5, 1.0, 1.0 );
// returns NaN
If provided a negative a, the function returns NaN.
javascript
var y = betainc( 0.5, -2.0, 2.0 );
// returns NaN
If provided a negative b, the function returns NaN.
javascript
var y = betainc( 0.5, 2.0, -2.0 );
// returns NaN
javascript
var randu = require( '@stdlib/random-base-randu' );
var betainc = require( '@stdlib/math-base-special-betainc' );
var i;
var x;
var a;
var b;
for ( i = 0; i < 100; i++ ) {
x = randu();
a = randu() * 10.0;
b = randu() * 10.0;
console.log( 'x: %d, \t a: %d, \t b: %d, \t f(x,a,b): %d', x.toFixed( 4 ), a.toFixed( 4 ), b.toFixed( 4 ), betainc( x, a, b ).toFixed( 4 ) );
}
@stdlib/math-base/special/beta][@stdlib/math/base/special/beta]: beta function.
- [@stdlib/math-base/special/betaincinv][@stdlib/math/base/special/betaincinv]: inverse incomplete beta function.
- [@stdlib/math-base/special/betaln][@stdlib/math/base/special/betaln]: natural logarithm of the beta function.
