digamma

Digamma function.

The digamma function ψ is the logarithmic derivative of the gamma function, i.e.

Installation

$ npm install math-digamma

Usage

var digamma = require( 'math-digamma' );

digamma( x )

Evaluates the digamma function.

var v = digamma( -2.5 );
// returns ~1.103

v = digamma( 1 );
// returns ~-0.577

v = digamma( 10 );
// returns ~2.252

If x is 0 or a negative integer, the function returns NaN.

var v = digamma( 0 );
// returns NaN

v = digamma( -1 );
// returns NaN

v = digamma( -2 );
// returns NaN

If provided NaN, the function returns NaN.

var v = digamma( NaN );
// returns NaN

Examples

var digamma = require( 'math-digamma' );

var x;
var v;
var i;

for ( i = 0; i < 10; i++ ) {
	x = Math.random()*10 - 5;
	v = digamma( x );
	console.log( 'x: %d, f(x): %d', x, v );
}

To run the example code from the top-level application directory,

$ node ./examples/index.js

Tests

Unit

This repository uses tape for unit tests. To run the tests, execute the following command in the top-level application directory:

$ make test

All new feature development should have corresponding unit tests to validate correct functionality.

Test Coverage

This repository uses Istanbul as its code coverage tool. To generate a test coverage report, execute the following command in the top-level application directory:

$ make test-cov

Istanbul creates a ./reports/coverage directory. To access an HTML version of the report,

$ make view-cov

Browser Support

This repository uses Testling for browser testing. To run the tests in a (headless) local web browser, execute the following command in the top-level application directory:

$ make test-browsers

To view the tests in a local web browser,

$ make view-browser-tests

License

MIT license.

Copyright

Copyright © 2016. The Compute.io Authors.