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/* f2z.cc
Mark Woolrich & Mark Jenkinson, FMRIB Image Analysis Group
Copyright (C) 1999-2000 University of Oxford */
/* CCOPYRIGHT */
#include <cmath>
#include "f2z.h"
#include "Log.h"
#include "tracer_plus.h"
#include <stdexcept>
#include "libprob.h"
using namespace NEWMAT;
using namespace Utilities;
namespace MISCMATHS {
F2z* F2z::f2z = NULL;
float F2z::largef2logp(float f, int d1, int d2)
{
Tracer_Plus ts("F2z::largef2logp");
// no of iterations:
int N = 20;
if (f<=0.0) {
cerr << "f cannot be zero or negative!" << endl;
return 0.0;
}
if (d1<=0 || d2<=0) {
cerr << "DOFs cannot be zero or negative!" << endl;
return 0.0;
}
double alpha=d1/(double)d2;
double m=(d1+d2)/2.0;
double n=(1-d1/2.0);
double loggam = (d1/2.0)*(::log(d1/(double)d2)-logbeta(d2/2.0,d1/2.0));
//iter=f^(-n)/(alpha*(n+m-1)) + n*f^(-(n+1))/(alpha^2*(n+m-1)*(n+m)) + n*(n+1)*f^(-(n+2))/(alpha^3*(n+m-1)*(n+m)*(n+m+1));
double top = 1.0;
double bot = n+m-1;
double iter = 0.0;
// cerr << "logbeta(d2/2.0,d1/2.0)=" << logbeta(d2/2.0,d1/2.0) << endl;
// cerr << "loggam = " << loggam << endl;
// cerr << "n = " << n << endl;
// cerr << "m = " << m << endl;
for(int i = 1; i <= N; i++)
{
// cerr << "i=" << i;
iter = iter + top*::pow(f,(-(n+i-1)))/(::pow(alpha,i)*bot);
top = top*(n-1+i)*(-1);
bot = bot*(n+m-1+i);
}
float logp = loggam-(m-1)*(::log(1+alpha*f))+::log(iter);
// cerr << "iter = " << iter << endl;
// cerr << "logp = " << logp << endl;
return logp;
}
bool F2z::islargef(float f, int d1, int d2, float &logp) {
if(f > 1.0 && d1>1)
{
logp=largef2logp(f,d1,d2);
return issmalllogp(logp);
}
else
return false;
}
bool F2z::issmalllogp(float logp) {
return (logp < -14.5);
}
float F2z::convert(float f, int d1, int d2)
{
Tracer_Plus ts("F2z::convert");
float z = 0.0, logp=0.0;
if(!islargef(f,d1,d2,logp)) {
double p = MISCMATHS::fdtr(d1, d2, f);
z = MISCMATHS::ndtri(p);
}
else {
z = logp2largez(logp);
}
return z;
}
void F2z::ComputeFStats(const ColumnVector& p_fs, int p_dof1, int p_dof2, ColumnVector& p_zs)
{
ColumnVector dof2 = p_fs;
dof2 = p_dof2;
ComputeFStats(p_fs,p_dof1,dof2,p_zs);
}
void F2z::ComputeFStats(const ColumnVector& p_fs, int p_dof1, const ColumnVector& p_dof2, ColumnVector& p_zs)
{
Tracer_Plus ts("F2z::ComputeFStats");
int numTS = p_fs.Nrows();
p_zs.ReSize(numTS);
F2z& f2z = F2z::getInstance();
for(int i = 1; i <= numTS; i++)
{
// cerr << "i=" << i << endl;
// cerr << "p_fs(i)=" << p_fs(i) << endl;
// cerr << "p_dof1=" << p_dof1 << endl;
// cerr << "p_dof2=" << p_dof2 << endl;
if (p_fs(i) > 0.0)
{
p_zs(i) = f2z.convert(p_fs(i),p_dof1,p_dof2(i));
}
else
{
p_zs(i) = 0.0;
}
}
}
}