expit

Compute the standard logistic function.

The standard logistic function, also called the expit function, inverse logit, or sigmoid function, is defined as the logistic function with parameters (k = 1, x0 = 0, L = 1).

Usage

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

expit( x )

Computes the standard logistic function.

var v = expit( 0.0 );
// returns ~0.5

v = expit( 1.0 );
// returns ~0.731

v = expit( -1.0 );
// returns ~0.269

v = expit( Infinity );
// returns 1.0

v = expit( NaN );
// returns NaN

Examples

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

var x;
var i;

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

C APIs

Usage

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

stdlib_base_expit( x )

Computes the standard logistic function.

double out = stdlib_base_expit( 0.0 );
// returns ~0.5

out = stdlib_base_expit( 1.0 );
// returns ~0.731

The function accepts the following arguments:

x: [in] double input value.

double stdlib_base_expit( const double x );

Examples

#include "stdlib/math/base/special/expit.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_expit( x );
        printf( "expit(%lf) = %lf\n", x, v );
    }
}