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+c function agauss.f
+c
+c source
+c   Bevington, page 48.
+c
+c purpose
+c   evaluate integral of gaussian probability function
+c
+c usage
+c   result = agauss (x, averag, sigma)
+c
+c description of parameters
+c   x      - limit for integral
+c   averag - mean of distribution
+c   sigma  - standard deviation of distribution
+c   integration range is averag +/- z*sigma
+c      where z = abs(x-averag)/sigma
+c
+c subroutines and function subprograms required
+c   none
+c
+	function agauss (x,averag,sigma)
+	double precision z,y2,term,sum,denom
+11	z=abs(x-averag)/sigma
+	agauss=0.
+	if (z) 42,42,21
+21	term=0.7071067812*z
+22	sum=term
+	y2=(z**2)/2.
+	denom=1.
+c
+c accumulate sums of terms
+c
+31	denom=denom+2.
+32	term=term*(y2*2./denom)
+33	sum=sum+term
+	if (term/sum-1.e-10) 41,41,31
+41	agauss=1.128379167*sum*dexp(-y2)
+42	return
+	end