Trigamma
Trigamma function.
The trigamma function ψ^(1) is the derivative of the digamma function.
Usage
var trigamma = require( '@stdlib/math/base/special/trigamma' );
trigamma( x )
Evaluates the trigamma function.
var v = trigamma( -2.5 );
// returns ~9.539
v = trigamma( 1.0 );
// returns ~1.645
v = trigamma( 10.0 );
// returns ~0.105
If x is 0 or a negative integer, the function returns NaN.
var v = trigamma( 0.0 );
// returns NaN
v = trigamma( -1.0 );
// returns NaN
v = trigamma( -2.0 );
// returns NaN
If provided NaN, the function returns NaN.
var v = trigamma( NaN );
// returns NaN
Examples
var randu = require( '@stdlib/random/base/randu' );
var trigamma = require( '@stdlib/math/base/special/trigamma' );
var x;
var v;
var i;
for ( i = 0; i < 10; i++ ) {
x = (randu()*100.0) - 50.0;
v = trigamma( x );
console.log( 'x: %d, ψ^(1)(x): %d', x, v );
}
C APIs
Usage
#include "stdlib/math/base/special/trigamma.h"
stdlib_base_trigamma( x )
Evaluates the trigamma function.
double out = stdlib_base_trigamma( -2.5 );
// returns ~9.539
out = stdlib_base_trigamma( 1.0 );
// returns ~1.645
The function accepts the following arguments:
- x:
[in] doubleinput value.
double stdlib_base_trigamma( const double x );
Examples
#include "stdlib/math/base/special/trigamma.h"
#include <stdio.h>
int main( void ) {
const double x[] = { 4.0, -1.5, -0.5, 0.5 };
double y;
int i;
for ( i = 0; i < 4; i++ ) {
y = stdlib_base_trigamma( x[ i ] );
printf( "trigamma(%lf) = %lf\n", x[ i ], y );
}
}