npm install math-evalpolyevalpoly
===
[![NPM version][npm-image]][npm-url] [![Build Status][build-image]][build-url] [![Coverage Status][coverage-image]][coverage-url] [![Dependencies][dependencies-image]][dependencies-url]
> Evaluates a [polynomial][polynomial].
Installation
`` bash`
$ npm install math-evalpoly
Usage
` javascript`
var evalpoly = require( 'math-evalpoly' );
#### evalpoly( c, x )
Evaluates a [polynomial][polynomial] having coefficients c and degree n at a value x, where n = c.length-1.
` javascript`
var v = evalpoly( [3,2,1], 10 );
// returns 123 => 310^0 + 210^1 + 1*10^2
The coefficients should be ordered in __ascending__ degree. For example, for a [polynomial][polynomial]
the coefficients would be
`
[c_0, c_1, ..., c_(n-1), c_n]
matching the summation notation.
#### evalpoly.factory( c )
Uses code generation to in-line coefficients and return a reusable function for evaluating a [polynomial][polynomial].
` javascript
var poly = evalpoly.factory( [3,2,1] );
var v = poly( 10 );
// returns 123 => 310^0 + 210^1 + 1*10^2
v = poly( 5 );
// returns 38 => 35^0 + 25^1 + 1*5^2
`
__Note__: For hot code paths in which coefficients are invariant, the generated function will be more performant than the main export.
Examples
` javascript
var round = require( 'math-round' );
var evalpoly = require( 'math-evalpoly' );
var coef;
var sign;
var poly;
var v;
var i;
// Create an array of random coefficients...
coef = new Float64Array( 10 );
for ( i = 0; i < coef.length; i++ ) {
if ( Math.random() < 0.5 ) {
sign = -1;
} else {
sign = 1;
}
coef[ i ] = sign round( Math.random()100 );
}
// Evaluate the polynomial at random values...
for ( i = 0; i < 100; i++ ) {
v = Math.random() * 100;
console.log( 'f(%d) = %d', v, evalpoly( coef, v ) );
}
// Generate an evalpoly function...`
poly = evalpoly.factory( coef );
for ( i = 0; i < 100; i++ ) {
v = Math.random()*100 - 50;
console.log( 'f(%d) = %d', v, poly( v ) );
}
To run the example code from the top-level application directory,
` bash`
$ node ./examples/index.js
---
Tests
$3
This repository uses [tape][tape] for unit tests. To run the tests, execute the following command in the top-level application directory:
` bash`
$ make test
All new feature development should have corresponding unit tests to validate correct functionality.
$3
This repository uses [Istanbul][istanbul] as its code coverage tool. To generate a test coverage report, execute the following command in the top-level application directory:
` bash`
$ make test-cov
Istanbul creates a ./reports/coverage directory. To access an HTML version of the report,
` bash`
$ make view-cov
$3
This repository uses [Testling][testling] for browser testing. To run the tests in a (headless) local web browser, execute the following command in the top-level application directory:
` bash`
$ make test-browsers
To view the tests in a local web browser,
` bash``
$ make view-browser-tests
---
License
Copyright
Copyright © 2016. The [Compute.io][compute-io] Authors..
[npm-image]: http://img.shields.io/npm/v/math-evalpoly.svg
[npm-url]: https://npmjs.org/package/math-evalpoly
[build-image]: http://img.shields.io/travis/math-io/evalpoly/master.svg
[build-url]: https://travis-ci.org/math-io/evalpoly
[coverage-image]: https://img.shields.io/codecov/c/github/math-io/evalpoly/master.svg
[coverage-url]: https://codecov.io/github/math-io/evalpoly?branch=master
[dependencies-image]: http://img.shields.io/david/math-io/evalpoly.svg
[dependencies-url]: https://david-dm.org/math-io/evalpoly
[dev-dependencies-image]: http://img.shields.io/david/dev/math-io/evalpoly.svg
[dev-dependencies-url]: https://david-dm.org/dev/math-io/evalpoly
[github-issues-image]: http://img.shields.io/github/issues/math-io/evalpoly.svg
[github-issues-url]: https://github.com/math-io/evalpoly/issues
[tape]: https://github.com/substack/tape
[istanbul]: https://github.com/gotwarlost/istanbul
[testling]: https://ci.testling.com
[polynomial]: https://en.wikipedia.org/wiki/Polynomial
[compute-io]: https://github.com/compute-io