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bisect.js
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bisect.js
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import sign from "./sign.js";
/**
* [Bisection method](https://en.wikipedia.org/wiki/Bisection_method) is a root-finding
* method that repeatedly bisects an interval to find the root.
*
* This function returns a numerical approximation to the exact value.
*
* @param {Function} func input function
* @param {number} start - start of interval
* @param {number} end - end of interval
* @param {number} maxIterations - the maximum number of iterations
* @param {number} errorTolerance - the error tolerance
* @returns {number} estimated root value
* @throws {TypeError} Argument func must be a function
*
* @example
* bisect(Math.cos,0,4,100,0.003); // => 1.572265625
*/
function bisect(func, start, end, maxIterations, errorTolerance) {
if (typeof func !== "function")
throw new TypeError("func must be a function");
for (let i = 0; i < maxIterations; i++) {
const output = (start + end) / 2;
if (
func(output) === 0 ||
Math.abs((end - start) / 2) < errorTolerance
) {
return output;
}
if (sign(func(output)) === sign(func(start))) {
start = output;
} else {
end = output;
}
}
throw new Error("maximum number of iterations exceeded");
}
export default bisect;