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/* Copyright (C) 2016 - IIT Bombay - FOSSEE
This file must be used under the terms of the CeCILL.
This source file is licensed as described in the file COPYING, which
you should have received as part of this distribution. The terms
are also available at
http://www.cecill.info/licences/Licence_CeCILL_V2-en.txt
Author: Brijesh Gupta C R
Organization: FOSSEE, IIT Bombay
Email: toolbox@scilab.in
*/
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include "erfinv.h"
# define PI 3.1415927
double derfinvs (double inp1)
{
double a[] = {0.88622692374517353,-1.6601283962374516,0.92661860147244357,-0.14110320437680104};
double b[] = {-2.13505380615258078,1.46060340345661088,-0.33198239813321595,0.01197270616590528};
double c[] = {-1.994216456587148,-1.87267416351196,3.60874665878559364,1.82365845766309853};
double d[] = {3.74146294065960872,1.81848952562894617};
if ((inp1 > 1) || (inp1 < -1))
{
return 0.0/0.0;
}
if ((inp1 >= -0.7) && (inp1 <= 0.7))
{
double sq = inp1 * inp1;
return (inp1 * (((a[3]*sq+a[2]) * sq+a[1]) * sq+a[0]) / ((((b[3]*sq+b[2]) * sq+b[1]) * sq+b[0]) * sq+1));
}
else if ((inp1 > 0.7) && (inp1 < 1))
{
double z = sqrt(-log((1-inp1)/2));
return ((((c[3]*z+c[2]) * z+c[1]) * z+c[0]) / ((d[1]*z+d[0]) * z+1));
}
else if ((inp1 > -1) && (inp1 < 0.7))
{
double z = sqrt(-log((1+inp1)/2));
return (-(((c[3]*z+c[2]) * z+c[1]) * z+c[0]) / ((d[1]*z+d[0]) * z+1));
}
}
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