Nyholm\EffectiveInterest\NewtonRaphson

Complexity

Total Complexity

3

Size/Duplication

Total Lines	33
Duplicated Lines	0 %

Coupling/Cohesion

Components	1
Dependencies	0

Test Coverage

Coverage

100%

Importance

Changes

0

2 Methods

Rating	Name	Duplication	Size	Complexity
A	__construct()	0	4	1
A	run()	0	10	2

<?php

declare(strict_types=1);

namespace Nyholm\EffectiveInterest;

/**
 * Newton-Raphsons method to do a numerical analysis to find the effective interest.
 *
 * {@link https://en.wikipedia.org/wiki/Newton%27s_method}
 *
 * @author Tobias Nyholm <tobias.nyholm@gmail.com>
 */
final class NewtonRaphson
{
    /**
     * @var int
     */
    private $precision;

    /**
     * @param int $precision The number of decimals to care to calculate
     */
    public function __construct(int $precision = 7)
    {
        $this->precision = $precision;
    }

    /**
     * @param callable $fx
     * @param callable $fdx
     * @param float    $guess
     *
     * @return float
     */
    public function run(callable $fx, callable $fdx, float $guess): float
    {
        $errorLimit = pow(10, -1 * $this->precision);
        do {
            $previousValue = $guess;
            $guess = $previousValue - ($fx($guess) / $fdx($guess));
        } while (abs($guess - $previousValue) > $errorLimit);

        return $guess;
    }
}