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math-erfinv

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erfinv

$NPM version$ $Build Status$ $Coverage Status$ $Dependencies$

Inverse error function.

The inverse error function is defined in terms of the Maclaurin series

$Inverse error function.$

where c_0 = 1 and

$Series coefficients.$

Installation

$ npm install math-erfinv

Usage

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

erfinv( x )

Evaluates the inverse error function.

var y = erfinv( 0.5 );
// returns ~0.4769

y = erfinv( 0.8 );
// returns ~0.9062

y = erfinv( -1 );
// returns -infinity

y = erfinv( 1 );
// returns +infinity

The domain of x is restricted to [-1,1]. If |x| > 1, the function will throw a RangeError.

var y = erfinv( -3.14 );
// throws <Error>

If provided NaN, the function returns NaN.

var y = erfinv( NaN );
// returns NaN

The inverse error function is an odd function; i.e., erfinv(-x) = -erfinv(x). Thus, in accordance with the IEEE 754 standard, if provided -0, the function returns -0.

var y = erfinv( -0 );
// returns -0

Examples

var linspace = require( 'compute-linspace' );
var erfinv = require( 'math-erfinv' );

var x = linspace( -1, 1, 100 );
var y;
var i;

for ( i = 0; i < x.length; i++ ) {
    y = erfinv( x[ i ] );
    console.log( 'x: %d, erfinv(x): %d', x[ i ], y );
}

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.

math-erfinv