venny/bin/fmin/bisect.js

Declarative Venn diagrams

// Code adapted from https://github.com/benfred/fmin
/** finds the zeros of a function, given two starting points (which must
 * have opposite signs */
export function bisect(f, a, b, parameters) {
    parameters = parameters || {};
    const maxIterations = parameters.maxIterations || 100, tolerance = parameters.tolerance || 1e-10, fA = f(a), fB = f(b);
    let delta = b - a;
    if (fA * fB > 0) {
        throw new Error('Initial bisect points must have opposite signs');
    }
    if (fA === 0)
        return a;
    if (fB === 0)
        return b;
    for (let i = 0; i < maxIterations; ++i) {
        delta /= 2;
        const mid = a + delta, fMid = f(mid);
        if (fMid * fA >= 0) {
            a = mid;
        }
        if ((Math.abs(delta) < tolerance) || (fMid === 0)) {
            return mid;
        }
    }
    return a + delta;
}