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Normal Distribution with PHP

south_paw
south_paw asked
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Last Modified: 2007-12-19
Anyone know how to find the normal distribution value using PHP?  I have mean, std dev, and the z-score.

Excel finds it via NORMSDIST(z).  I want to hand code it, something like:

$normdist($zScore) = //calc for norms

Or would I be better off using javascript?

Any ideas appreciated.  
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Author

Commented:
I found this on the web, I'm going to try to convert it....

Help appreciated!


Function u_SNorm(z)

    c1 = 2.506628
    c2 = 0.3193815
    c3 = -0.3565638
    c4 = 1.7814779
    c5 = -1.821256
    c6 = 1.3302744
    If z > 0 Or z = 0 Then
              w = 1
    Else: w = -1
    End If
    y = 1 / (1 + 0.2316419 * w * z)
    u_SNorm = 0.5 + w * (0.5 - (Exp(-z * z / 2) / c1) * _
            (y * (c2 + y * (c3 + y * (c4 + y * (c5 + y * c6))))))
           
End Function

Author

Commented:
I think i just answered my on Qeustion:

      $c1 = 2.506628;
    $c2 = 0.3193815;
    $c3 = -0.3565638;
    $c4 = 1.7814779;
    $c5 = -1.821256;
    $c6 = 1.3302744;
    if ($z1 > 0 )
             $w = 1;
    else $w = -1;
   
    $y = 1 / (1 + 0.2316419 * $w * $z1);
    $normDist = 0.5 + $w * (0.5 - (exp(-$z1 * $z1 / 2) / $c1) * _
            ($y * ($c2 + $y * ($c3 + $y * ($c4 + $y * ($c5 + $y * $c6))))));
                  
                  echo $normDist;

Author

Commented:
Please close Q and refund points, I solved all by my lelf.
CERTIFIED EXPERT
Top Expert 2006

Commented:
You can request a refund by posting in the community support area. See the "support" link in the topright menu.

-r-
Commented:
Closed, 500 points refunded.
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