Numeric Derivative

numeric_derivative.js

function derivator(func, step) {

    step = step || Number.MIN_VALUE;

    return function (x) {
        return (func(x + step) - func(x)) / step;
    };
}


// As simple as that.
//
// var derive = derivator(function(x) { return x * x; }, 1e-10);
//
// derive(1) now (approximately) equals the derivative of x^2 for x = 1. The smaller the step,
// the closer the approximation.