Impala Documentation

double Impala::Visualization::Plot::Weibull::GammaFunc ( double xx ) [inline, protected]

Definition at line 97 of file Function.h.

00098     {
00099         // I could only find a log gamma from "numerical recipes"
00100         // http://www.library.cornell.edu/nr/cbookcpdf.html
00101         double x,y,tmp,ser;
00102         static double cof[6] =
00103         {
00104             76.18009172947146, -86.50532032941677,
00105             24.01409824083091, -1.231739572450155,
00106             0.1208650973866179e-2, -0.5395239384953e-5
00107         };
00108 
00109         int j;
00110         y=x=xx;
00111         tmp=x+5.5;
00112         tmp -= (x+0.5)*log(tmp);
00113         ser=1.000000000190015;
00114         for (j=0;j<=5;j++)
00115             ser += cof[j]/++y;
00116         xx = -tmp+log(2.5066282746310005*ser/x);
00117         return exp(xx);
00118     }