lagrange

node-lagrange
=============

Implements Lagrange polynomial interpolation for both the numbers you are used
to as well as finite fields. Given a list of x values and a list of y values,
it will attempt to solve f(x) for a given x value.

All finite field arithmetic uses the
galois NPM module (npm show
galois).

Functions
---------

- base10(x, xValues, yValues) - Assumes the standard decimal system.

- galois(x, xValues, yValues, gfW) - The gfW parameter is passed to the
galois module functions, which uses it as the exponent to define the
field size (2^w).

- splitCoords(coords) - The above math functions take two separate arrays,
one for x values and one for y values, but your application is likely to
use an array of tuples to define coordinates. This utility function splits
them out, giving you a tuple of x and y values ([xValues, yValues]).

Examples
--------

See ./tests/lagrange.js for examples using different equations.

``javascript
var lagrange = require('lagrange');

var GF_W = 8;

//f(x)=2x, for GF(256)
var coords = [[5, 10], [244, 245]]; //app stores tuples
coords = lagrange.splitCoords(coords); //make them lagrange friendly

assert.equal(lagrange.galois(0, coords[0], coords[1], GF_W), 0);
assert.equal(lagrange.galois(255, coords[0], coords[1], GF_W), 227);
console.log('success');
``