logit

Compute the logit function.

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

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

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

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 uniform = require( '@stdlib/random/array/uniform' );
var logEachMap = require( '@stdlib/console/log-each-map' );
var logit = require( '@stdlib/math/base/special/logit' );

var opts = {
    'dtype': 'float64'
};
var p = uniform( 100, 0.0, 1.0, opts );

logEachMap( 'logit(%0.4f) = %0.4f', p, logit );

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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 );
    }
}