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// $Id: gammaUtilities.cpp 962 2006-11-07 15:13:34Z privmane $
#include "gammaUtilities.h"
#include "logFile.h"
#include "errorMsg.h"
#include <cmath>
//gser: returns the incomplete Gamma function evaluated by its series representation
void gser(MDOUBLE *gamser, MDOUBLE a, MDOUBLE x, MDOUBLE *gln)
{
//MDOUBLE gammln(MDOUBLE xx);
int n;
MDOUBLE sum,del,ap;
*gln=gammln(a);
if (x <= 0.0) {
if (x < 0.0) LOG(1,<<"x less than 0 in routine gser");
*gamser=0.0;
return;
} else {
ap=a;
del=sum=1.0/a;
for (n=1;n<=ITMAX;n++) {
++ap;
del *= x/ap;
sum += del;
if (fabs(del) < fabs(sum)*EPS) {
*gamser=sum*exp(-x+a*log(x)-(*gln));
return;
}
}
LOG(1,<<"Too many interations in routine gser");
return;
}
}
//gcf: returns the complement of the incomplete Gamma function evaluated by its continued fraction representation
void gcf(MDOUBLE *gammcf, MDOUBLE a, MDOUBLE x, MDOUBLE *gln)
{
//MDOUBLE gammln(MDOUBLE xx);
int i;
MDOUBLE an,b,c,d,del,h;
*gln=gammln(a);
b=x+1.0-a;
c=1.0/FPMIN;
d=1.0/b;
h=d;
for (i=1;i<=ITMAX;i++) {
an = -i*(i-a);
b += 2.0;
d=an*d+b;
if (fabs(d) < FPMIN) d=FPMIN;
c=b+an/c;
if (fabs(c) < FPMIN) c=FPMIN;
d=1.0/d;
del=d*c;
h *= del;
if (fabs(del-1.0) < EPS) break;
}
if (i > ITMAX) LOG(1,<<"a too large, ITMAX too small in gcf");
*gammcf=exp(-x+a*log(x)-(*gln))*h;
}
//gammp(a, x): computes the incomplete Gamma function which is:
// 1/Gamma(a) * (the integral from 0 to x of (t^(a-1)*e^(-t)) dt)
//gammp can be computed in two different ways: by a series representation (gser(..))
//or by a continued fraction representation (gcf(..))
//gammp chooses to function will be used, according to the values of a and x
MDOUBLE gammp(MDOUBLE a, MDOUBLE x)
{
//void gcf(MDOUBLE *gammcf, MDOUBLE a, MDOUBLE x, MDOUBLE *gln);
//void gser(MDOUBLE *gamser, MDOUBLE a, MDOUBLE x, MDOUBLE *gln);
MDOUBLE gamser,gammcf,gln;
if (x < 0.0 || a <= 0.0) LOG(1,<<"Invalid arguments in routine gammp");
if (x < (a+1.0)) {
gser(&gamser,a,x,&gln);
return gamser;
} else {
gcf(&gammcf,a,x,&gln);
return 1.0-gammcf;
}
}
//I add////////////
MDOUBLE gammq(MDOUBLE a, MDOUBLE x)
{
void gcf(MDOUBLE *gammcf, MDOUBLE a, MDOUBLE x, MDOUBLE *gln);
void gser(MDOUBLE *gamser, MDOUBLE a, MDOUBLE x, MDOUBLE *gln);
MDOUBLE gamser,gammcf,gln;
if (x < 0.0 || a <= 0.0) LOG(1,<<"Invalid arguments in routine gammp");
if (x < (a+1.0)) {
gser(&gamser,a,x,&gln);
return 1.0 - gamser;
} else {
gcf(&gammcf,a,x,&gln);
return gammcf;
}
}
/*************************************************************************
// this function computed the ln of the gamma function
// The Gamma funnction: Gamma(xx) = integral from 0 to infinity of (t^(xx-1)*e^(-t)) dt.
*************************************************************************/
MDOUBLE gammln(MDOUBLE xx)
{
MDOUBLE x,y,tmp,ser;
static MDOUBLE cof[6]={
static_cast<MDOUBLE>(76.18009172947146),
static_cast<MDOUBLE>(-86.50532032941677),
static_cast<MDOUBLE>(24.01409824083091),
static_cast<MDOUBLE>(-1.231739572450155),
static_cast<MDOUBLE>(0.1208650973866179e-2),
static_cast<MDOUBLE>(-0.5395239384953e-5)
};
int j;
y=x=xx;
tmp=x+5.5;
tmp -= (x+0.5)*log(tmp);
ser=1.000000000190015f;
for (j=0;j<6;j++) ser += cof[j]/++y;
return -tmp+log(2.5066282746310005*ser/x);
}
//
MDOUBLE search_for_z_in_dis_with_any_beta(MDOUBLE alpha,MDOUBLE beta, MDOUBLE ahoson)
{
return (search_for_z_in_dis_with_beta_1(alpha,ahoson)/beta);
}
MDOUBLE search_for_z_in_dis_with_beta_1(MDOUBLE alpha, MDOUBLE ahoson)
{
if ( ahoson>1 || ahoson<0 ) errorMsg::reportError("Error in function search_for_z_in_dis_with_beta_1");
MDOUBLE left=0;
MDOUBLE right=99999.0;
MDOUBLE tmp=5000.0;
MDOUBLE results=0.0;
for (int i=0;i<100000000 ; i++)
{
results=gammp(alpha,tmp);
if (fabs(ahoson-results)<ERR_FOR_GAMMA_CALC) {
return tmp;
}
if (results>ahoson) {
right=tmp;
}
else left=tmp;
tmp=(right+left)/2;
}
cout << "ERROR in search_for_z_in_dis_with_beta_1() Alpha is: "<< alpha <<endl;
errorMsg::reportError("Error in function search_for_z_in_dis_with_beta_1 - first bonderi is 0");// also quit the program
return 0;
}
MDOUBLE the_avarage_r_in_category_between_a_and_b(MDOUBLE left, MDOUBLE right, MDOUBLE alpha, MDOUBLE beta, int k)
{// and and b are the border of percentile k)
MDOUBLE tmp;
tmp= gammp(alpha+1,right*beta) - gammp(alpha+1,left*beta);
tmp= (tmp*alpha/beta)*k;
return tmp;
}
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