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Excel RATE() Javascript Function
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/*! | |
* @fileOverview Finance Excel Rate Formula Javascript Equivalent | |
* @version 1.0.0 | |
* | |
* @author Burak Arslan @kucukharf http://www.github.com/kucukharf | |
* @license | |
* Copyright (c) 2010-2018 Burak Arslan | |
* Licensed under Creative Commons (CC) license | |
* @usage RATE($periods, $payment, $present, $future, $type, $guess) | |
*/ | |
RATE = function(periods, payment, present, future, type, guess) { | |
guess = (guess === undefined) ? 0.01 : guess; | |
future = (future === undefined) ? 0 : future; | |
type = (type === undefined) ? 0 : type; | |
// Set maximum epsilon for end of iteration | |
var epsMax = 1e-10; | |
// Set maximum number of iterations | |
var iterMax = 10; | |
// Implement Newton's method | |
var y, y0, y1, x0, x1 = 0, | |
f = 0, | |
i = 0; | |
var rate = guess; | |
if (Math.abs(rate) < epsMax) { | |
y = present * (1 + periods * rate) + payment * (1 + rate * type) * periods + future; | |
} else { | |
f = Math.exp(periods * Math.log(1 + rate)); | |
y = present * f + payment * (1 / rate + type) * (f - 1) + future; | |
} | |
y0 = present + payment * periods + future; | |
y1 = present * f + payment * (1 / rate + type) * (f - 1) + future; | |
i = x0 = 0; | |
x1 = rate; | |
while ((Math.abs(y0 - y1) > epsMax) && (i < iterMax)) { | |
rate = (y1 * x0 - y0 * x1) / (y1 - y0); | |
x0 = x1; | |
x1 = rate; | |
if (Math.abs(rate) < epsMax) { | |
y = present * (1 + periods * rate) + payment * (1 + rate * type) * periods + future; | |
} else { | |
f = Math.exp(periods * Math.log(1 + rate)); | |
y = present * f + payment * (1 / rate + type) * (f - 1) + future; | |
} | |
y0 = y1; | |
y1 = y; | |
++i; | |
} | |
return rate; | |
}; | |
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