/* Gamma inverse cdf */
double icdfGamma (double y, double shape)
{
double result;
result = PointChi2 (y, 2.0*shape)/(2.0*shape);
/* to avoid -1.0 */
if (result < 0.0)
{
result = 0.0;
}
return result;
}
int main(int argc, char*argv[])
{
int i,j, n=20, ndf=200, nprob=8, option=0; /* 0:table, 1:prob */
double df,chi2, d=1.0/n, prob[]= {.005, .025, .1, .5, .90, .95, .99, .999};
option=(argc>1);
if (option) {
for (; ; ) {
printf ("\nd.f. & Chi^2 value (Ctrl-c to break)? ");
scanf ("%lf%lf", &df, &chi2);
if(df<1 || chi2<0) break;
prob[0]=1-CDFChi2(chi2,df);
printf ("\nprob = %.9f = %.3e\n", prob[0],prob[0]);
}
}
else {
printf ("\n\nChi-square critical values\n");
for (i=0; i<ndf; i++) {
if (i%15==0) {
printf ("\n\t\t\t\tSignificance level\n");
printf ("\n DF ");
for (j=0; j<nprob; j++) printf ("%9.4f", 1-prob[j]);
printf ("\n");
}
printf ("\n%3d ", i+1);
for (j=0; j<nprob; j++)
printf ("%9.4f", PointChi2(prob[j],(double)(i+1)));
if (i%5==4) printf ("\n");
if (i%15==14) {
printf ("\nENTER for more, (q+ENTER) for quit... ");
if (getchar()=='q') break;
}
}
}
printf ("\n");
return (0);
}
