evalpoly

Evaluate a polynomial.

A polynomial in a variable x can be expressed as

where c_n, c_{n-1}, ..., c_0 are constants.

Installation

npm install @stdlib/math-base-tools-evalpoly

Usage

var evalpoly = require( '@stdlib/math-base-tools-evalpoly' );

evalpoly( c, x )

Evaluates a polynomial having coefficients c and degree n at a value x, where n = c.length-1.

var v = evalpoly( [ 3.0, 2.0, 1.0 ], 10 ); // => 3*10^0 + 2*10^1 + 1*10^2
// returns 123.0

The coefficients should be ordered in ascending degree, thus matching summation notation.

evalpoly.factory( c )

Uses code generation to in-line coefficients and return a function for evaluating a polynomial.

var polyval = evalpoly.factory( [ 3.0, 2.0, 1.0 ] );

var v = polyval( 10.0 ); // => 3*10^0 + 2*10^1 + 1*10^2
// returns 123.0

v = polyval( 5.0 ); // => 3*5^0 + 2*5^1 + 1*5^2
// returns 38.0

Notes

• For hot code paths in which coefficients are invariant, a compiled function will be more performant than evalpoly().
• While code generation can boost performance, its use may be problematic in browser contexts enforcing a strict content security policy (CSP). If running in or targeting an environment with a CSP, avoid using code generation.

Examples

var randu = require( '@stdlib/random-base-randu' );
var round = require( '@stdlib/math-base-special-round' );
var Float64Array = require( '@stdlib/array-float64' );
var evalpoly = require( '@stdlib/math-base-tools-evalpoly' );

var polyval;
var coef;
var sign;
var v;
var i;

// Create an array of random coefficients...
coef = new Float64Array( 10 );
for ( i = 0; i < coef.length; i++ ) {
    if ( randu() < 0.5 ) {
        sign = -1.0;
    } else {
        sign = 1.0;
    }
    coef[ i ] = sign * round( randu()*100.0 );
}

// Evaluate the polynomial at random values...
for ( i = 0; i < 100; i++ ) {
    v = randu() * 100.0;
    console.log( 'f(%d) = %d', v, evalpoly( coef, v ) );
}

// Generate an `evalpoly` function...
polyval = evalpoly.factory( coef );
for ( i = 0; i < 100; i++ ) {
    v = (randu()*100.0) - 50.0;
    console.log( 'f(%d) = %d', v, polyval( v ) );
}

See Also

• @stdlib/math-base/tools/evalrational: evaluate a rational function.

Notice

This package is part of stdlib, a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

For more information on the project, filing bug reports and feature requests, and guidance on how to develop stdlib, see the main project repository.

Community

License

See LICENSE.

Copyright

Copyright © 2016-2024. The Stdlib Authors.