Probability Density Function

Uniform distribution probability density function (PDF).

The probability density function (PDF) for a continuous uniform random variable is

where a is the minimum support and b is the maximum support of the distribution. The parameters must satisfy a < b.

Installation

npm install @stdlib/stats-base-dists-uniform-pdf

Usage

var pdf = require( '@stdlib/stats-base-dists-uniform-pdf' );

pdf( x, a, b )

Evaluates the probability density function (PDF) for a continuous uniform distribution with parameters a (minimum support) and b (maximum support).

var y = pdf( 2.0, 0.0, 4.0 );
// returns 0.25

y = pdf( 5.0, 0.0, 4.0 );
// returns 0.0

y = pdf( 0.25, 0.0, 1.0 );
// returns 1.0

If provided NaN as any argument, the function returns NaN.

var y = pdf( NaN, 0.0, 1.0 );
// returns NaN

y = pdf( 0.0, NaN, 1.0 );
// returns NaN

y = pdf( 0.0, 0.0, NaN );
// returns NaN

If provided a >= b, the function returns NaN.

var y = pdf( 2.5, 3.0, 2.0 );
// returns NaN

y = pdf( 2.5, 3.0, 3.0 );
// returns NaN

pdf.factory( a, b )

Returns a function for evaluating the PDF of a continuous uniform distribution with parameters a (minimum support) and b (maximum support).

var myPDF = pdf.factory( 6.0, 7.0 );
var y = myPDF( 7.0 );
// returns 1.0

y = myPDF( 5.0 );
// returns 0.0

Examples

var randu = require( '@stdlib/random-base-randu' );
var pdf = require( '@stdlib/stats-base-dists-uniform-pdf' );

var a;
var b;
var x;
var y;
var i;

for ( i = 0; i < 25; i++ ) {
    x = (randu() * 20.0) - 10.0;
    a = (randu() * 20.0) - 20.0;
    b = a + (randu() * 40.0);
    y = pdf( x, a, b );
    console.log( 'x: %d, a: %d, b: %d, f(x;a,b): %d', x.toFixed( 4 ), a.toFixed( 4 ), b.toFixed( 4 ), y.toFixed( 4 ) );
}

C APIs

Usage

#include "stdlib/stats/base/dists/uniform/pdf.h"

stdlib_base_dists_uniform_pdf( x, a, b )

Evaluates the probability density function (PDF) for a continuous uniform distribution with parameters a (minimum support) and b (maximum support).

double out = stdlib_base_dists_uniform_pdf( 2.0, 0.0, 4.0 );
// returns 0.25

The function accepts the following arguments:

• x: [in] double input value.
• a: [in] double minimum support.
• b: [in] double maximum support.

double stdlib_base_dists_uniform_pdf( const double x, const double a, const double b );

Examples

#include "stdlib/stats/base/dists/uniform/pdf.h"
#include <stdlib.h>
#include <stdio.h>

static double random_uniform( const double min, const double max ) {
    double v = (double)rand() / ( (double)RAND_MAX + 1.0 );
    return min + ( v*(max-min) );
}

int main( void ) {
    double x;
    double a;
    double b;
    double y;
    int i;

    for ( i = 0; i < 25; i++ ) {
        x = random_uniform( -10.0, 10.0 );
        a = random_uniform( -20.0, 0.0 );
        b = random_uniform( a, a+40.0 );
        y = stdlib_base_dists_uniform_pdf( x, a, b );
        printf( "x: %lf, a: %lf, b: %lf, f(x;a,b): %lf\n", x, a, b, y );
    }
}

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 © 2016-2026. The Stdlib Authors.