SUBROUTINE gcf(gammcf,a,x,gln) INTEGER ITMAX REAL a,gammcf,gln,x,EPS,FPMIN PARAMETER (ITMAX=100,EPS=3.e-7,FPMIN=1.e-30) CU USES gammln INTEGER i REAL an,b,c,d,del,h,gammln gln=gammln(a) b=x+1.-a c=1./FPMIN d=1./b h=d do 11 i=1,ITMAX an=-i*(i-a) b=b+2. d=an*d+b if(abs(d).lt.FPMIN)d=FPMIN c=b+an/c if(abs(c).lt.FPMIN)c=FPMIN d=1./d del=d*c h=h*del if(abs(del-1.).lt.EPS)goto 1 11 continue pause 'a too large, ITMAX too small in gcf' 1 gammcf=exp(-x+a*log(x)-gln)*h return END C (C) Copr. 1986-92 Numerical Recipes Software .