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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
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