Nyholm\EffectiveInterest\NewtonRaphson

Complexity

Total Complexity

3

Size/Duplication

Total Lines	34
Duplicated Lines	0 %

Coupling/Cohesion

Components	1
Dependencies	0

Importance

Changes

0

2 Methods

Rating	Name	Duplication	Size	Complexity
A	__construct()	0	4	1
A	run()	0	11	2

<?php

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>
 */
class NewtonRaphson
{
    /**
     * @var int
     */
    private $precision;

    /**
     * @param int $precision
     */
    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
    {
        $newValue = $guess;
        $errorLimit = pow(10, -1 * $this->precision);
        do {
            $previousValue = $newValue;
            $newValue = $previousValue - ($fx($previousValue) / $fdx($previousValue));
        } while (abs($newValue - $previousValue) > $errorLimit);

        return $newValue * 12;
    }
}