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logit

Compute the logit function.

The logit function is defined as the logarithm of the odds p / (1-p); i.e.,

$$\mathop{\mathrm{logit}}(p)=\log \left({\frac {p}{1-p}}\right)$$

The logit function is the inverse of the standard logistic function, sometimes also called the sigmoid function.

Installation

npm install @stdlib/math-base-special-logit

Alternatively,

• To load the package in a website via a script tag without installation and bundlers, use the ES Module available on the esm branch (see README).
• If you are using Deno, visit the deno branch (see README for usage intructions).
• For use in Observable, or in browser/node environments, use the Universal Module Definition (UMD) build available on the umd branch (see README).

The branches.md file summarizes the available branches and displays a diagram illustrating their relationships.

To view installation and usage instructions specific to each branch build, be sure to explicitly navigate to the respective README files on each branch, as linked to above.

Usage

var logit = require( '@stdlib/math-base-special-logit' );

logit( p )

Computes the logit function.

var v = logit( 0.2 );
// returns ~-1.386

v = logit( 0.9 );
// returns ~2.197

If p < 0 or p > 1, the function returns NaN.

var v = logit( 1.3 );
// returns NaN

v = logit( -0.2 );
// returns NaN

Examples

var randu = require( '@stdlib/random-base-randu' );
var logit = require( '@stdlib/math-base-special-logit' );

var p;
var i;

for ( i = 0; i < 100; i++ ) {
    p = randu();
    console.log( 'logit(%d) = %d', p, logit( p ) );
}

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C APIs

Usage

#include "stdlib/math/base/special/logit.h"

stdlib_base_logit( p )

Computes the logit function.

double out = stdlib_base_logit( 0.2 );
// returns ~-1.386

out = stdlib_base_logit( 0.9 );
// returns ~2.197

The function accepts the following arguments:

• p: [in] double input value.

double stdlib_base_logit( const double p ); 

Examples

#include "stdlib/math/base/special/logit.h"
#include <stdlib.h>
#include <stdio.h>

int main( void ) {
    double x;
    double v;
    int i;

    for ( i = 0; i < 100; i++ ) {
        x = (double)rand() / (double)RAND_MAX;
        v = stdlib_base_logit( x );
        printf( "logit(%lf) = %lf\n", x, v );
    }
}

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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

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License

See LICENSE.

Copyright

Copyright © 2016-2024. The Stdlib Authors.