<?php
namespace PhpOffice\PhpSpreadsheet\Calculation\Financial\CashFlow\Variable;
use PhpOffice\PhpSpreadsheet\Calculation\Functions;
use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
class Periodic
{
const FINANCIAL_MAX_ITERATIONS = 128;
const FINANCIAL_PRECISION = 1.0e-08;
/**
* IRR.
*
* Returns the internal rate of return for a series of cash flows represented by the numbers in values.
* These cash flows do not have to be even, as they would be for an annuity. However, the cash flows must occur
* at regular intervals, such as monthly or annually. The internal rate of return is the interest rate received
* for an investment consisting of payments (negative values) and income (positive values) that occur at regular
* periods.
*
* Excel Function:
* IRR(values[,guess])
*
* @param mixed $values An array or a reference to cells that contain numbers for which you want
* to calculate the internal rate of return.
* Values must contain at least one positive value and one negative value to
* calculate the internal rate of return.
* @param mixed $guess A number that you guess is close to the result of IRR
*
* @return float|string
*/
public static function rate($values, $guess = 0.1)
{
if (!is_array($values)) {
return ExcelError::VALUE();
}
$values = Functions::flattenArray($values);
$guess = Functions::flattenSingleValue($guess);
// create an initial range, with a root somewhere between 0 and guess
$x1 = 0.0;
$x2 = $guess;
$f1 = self::presentValue($x1, $values);
$f2 = self::presentValue($x2, $values);
for ($i = 0; $i < self::FINANCIAL_MAX_ITERATIONS; ++$i) {
if (($f1 * $f2) < 0.0) {
break;
}
if (abs($f1) < abs($f2)) {
$f1 = self::presentValue($x1 += 1.6 * ($x1 - $x2), $values);
} else {
$f2 = self::presentValue($x2 += 1.6 * ($x2 - $x1), $values);
}
}
if (($f1 * $f2) > 0.0) {
return ExcelError::VALUE();
}
$f = self::presentValue($x1, $values);
if ($f < 0.0) {
$rtb = $x1;
$dx = $x2 - $x1;
} else {
$rtb = $x2;
$dx = $x1 - $x2;
}
for ($i = 0; $i < self::FINANCIAL_MAX_ITERATIONS; ++$i) {
$dx *= 0.5;
$x_mid = $rtb + $dx;
$f_mid = self::presentValue($x_mid, $values);
if ($f_mid <= 0.0) {
$rtb = $x_mid;
}
if ((abs($f_mid) < self::FINANCIAL_PRECISION) || (abs($dx) < self::FINANCIAL_PRECISION)) {
return $x_mid;
}
}
return ExcelError::VALUE();
}
/**
* MIRR.
*
* Returns the modified internal rate of return for a series of periodic cash flows. MIRR considers both
* the cost of the investment and the interest received on reinvestment of cash.
*
* Excel Function:
* MIRR(values,finance_rate, reinvestment_rate)
*
* @param mixed $values An array or a reference to cells that contain a series of payments and
* income occurring at regular intervals.
* Payments are negative value, income is positive values.
* @param mixed $financeRate The interest rate you pay on the money used in the cash flows
* @param mixed $reinvestmentRate The interest rate you receive on the cash flows as you reinvest them
*
* @return float|string Result, or a string containing an error
*/
public static function modifiedRate($values, $financeRate, $reinvestmentRate)
{
if (!is_array($values)) {
return ExcelError::DIV0();
}
$values = Functions::flattenArray($values);
$financeRate = Functions::flattenSingleValue($financeRate);
$reinvestmentRate = Functions::flattenSingleValue($reinvestmentRate);
$n = count($values);
$rr = 1.0 + $reinvestmentRate;
$fr = 1.0 + $financeRate;
$npvPos = $npvNeg = self::$zeroPointZero;
foreach ($values as $i => $v) {
if ($v >= 0) {
$npvPos += $v / $rr ** $i;
} else {
$npvNeg += $v / $fr ** $i;
}
}
if ($npvNeg === self::$zeroPointZero || $npvPos === self::$zeroPointZero) {
return ExcelError::DIV0();
}
$mirr = ((-$npvPos * $rr ** $n)
/ ($npvNeg * ($rr))) ** (1.0 / ($n - 1)) - 1.0;
return is_finite($mirr) ? $mirr : ExcelError::NAN();
}
/**
* Sop to Scrutinizer.
*
* @var float
*/
private static $zeroPointZero = 0.0;
/**
* NPV.
*
* Returns the Net Present Value of a cash flow series given a discount rate.
*
* @param mixed $rate
* @param array $args
*
* @return float
*/
public static function presentValue($rate, ...$args)
{
$returnValue = 0;
$rate = Functions::flattenSingleValue($rate);
$aArgs = Functions::flattenArray($args);
// Calculate
$countArgs = count($aArgs);
for ($i = 1; $i <= $countArgs; ++$i) {
// Is it a numeric value?
if (is_numeric($aArgs[$i - 1])) {
$returnValue += $aArgs[$i - 1] / (1 + $rate) ** $i;
}
}
return $returnValue;
}
}