/**
* BESSELJ
*
* Returns the Bessel function
*
* Excel Function:
* BESSELJ(x,ord)
*
* @access public
* @category Engineering Functions
* @param float $x The value at which to evaluate the function.
* If x is nonnumeric, BESSELJ returns the #VALUE! error value.
* @param integer $ord The order of the Bessel function. If n is not an integer, it is truncated.
* If $ord is nonnumeric, BESSELJ returns the #VALUE! error value.
* If $ord < 0, BESSELJ returns the #NUM! error value.
* @return float
*
*/
public static function BESSELJ($x, $ord)
{
$x = is_null($x) ? 0.0 : PHPExcel_Calculation_Functions::flattenSingleValue($x);
$ord = is_null($ord) ? 0.0 : PHPExcel_Calculation_Functions::flattenSingleValue($ord);
if (is_numeric($x) && is_numeric($ord)) {
$ord = floor($ord);
if ($ord < 0) {
return PHPExcel_Calculation_Functions::NaN();
}
$fResult = 0;
if (abs($x) <= 30) {
$fResult = $fTerm = pow($x / 2, $ord) / PHPExcel_Calculation_MathTrig::FACT($ord);
$ordK = 1;
$fSqrX = $x * $x / -4;
do {
$fTerm *= $fSqrX;
$fTerm /= $ordK * ($ordK + $ord);
$fResult += $fTerm;
} while (abs($fTerm) > 1.0E-12 && ++$ordK < 100);
} else {
$f_PI_DIV_2 = M_PI / 2;
$f_PI_DIV_4 = M_PI / 4;
$fXAbs = abs($x);
$fResult = sqrt(M_2DIVPI / $fXAbs) * cos($fXAbs - $ord * $f_PI_DIV_2 - $f_PI_DIV_4);
if ($ord & 1 && $x < 0) {
$fResult = -$fResult;
}
}
return is_nan($fResult) ? PHPExcel_Calculation_Functions::NaN() : $fResult;
}
return PHPExcel_Calculation_Functions::VALUE();
}
/**
* POISSON
*
* Returns the Poisson distribution. A common application of the Poisson distribution
* is predicting the number of events over a specific time, such as the number of
* cars arriving at a toll plaza in 1 minute.
*
* @param float $value
* @param float $mean Mean Value
* @param boolean $cumulative
* @return float
*
*/
public static function POISSON($value, $mean, $cumulative)
{
$value = PHPExcel_Calculation_Functions::flattenSingleValue($value);
$mean = PHPExcel_Calculation_Functions::flattenSingleValue($mean);
if (is_numeric($value) && is_numeric($mean)) {
if ($value <= 0 || $mean <= 0) {
return PHPExcel_Calculation_Functions::NaN();
}
if (is_numeric($cumulative) || is_bool($cumulative)) {
if ($cumulative) {
$summer = 0;
for ($i = 0; $i <= floor($value); ++$i) {
$summer += pow($mean, $i) / PHPExcel_Calculation_MathTrig::FACT($i);
}
return exp(0 - $mean) * $summer;
} else {
return exp(0 - $mean) * pow($mean, $value) / PHPExcel_Calculation_MathTrig::FACT($value);
}
}
}
return PHPExcel_Calculation_Functions::VALUE();
}
/**
* BESSELJ
*
* Returns the Bessel function
*
* @param float $x
* @param float $n
* @return int
*/
public static function BESSELJ($x, $n) {
$x = (is_null ( $x )) ? 0.0 : PHPExcel_Calculation_Functions::flattenSingleValue ( $x );
$n = (is_null ( $n )) ? 0.0 : PHPExcel_Calculation_Functions::flattenSingleValue ( $n );
if ((is_numeric ( $x )) && (is_numeric ( $n ))) {
$n = floor ( $n );
if ($n < 0) {
return PHPExcel_Calculation_Functions::NaN ();
}
$f_PI_DIV_2 = M_PI / 2;
$f_PI_DIV_4 = M_PI / 4;
$fResult = 0;
if (abs ( $x ) <= 30) {
$fTerm = pow ( $x / 2, $n ) / PHPExcel_Calculation_MathTrig::FACT ( $n );
$nK = 1;
$fResult = $fTerm;
$fSqrX = ($x * $x) / - 4;
do {
$fTerm *= $fSqrX;
$fTerm /= ($nK * ($nK + $n));
$fResult += $fTerm;
} while ( (abs ( $fTerm ) > 1e-10) && (++ $nK < 100) );
} else {
$fXAbs = abs ( $x );
$fResult = sqrt ( M_2DIVPI / $fXAbs ) * cos ( $fXAbs - $n * $f_PI_DIV_2 - $f_PI_DIV_4 );
if (($n && 1) && ($x < 0)) {
$fResult = - $fResult;
}
}
return $fResult;
}
return PHPExcel_Calculation_Functions::VALUE ();
} // function BESSELJ()
