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  • Committer: Package Import Robot
  • Author(s): Ole Streicher
  • Date: 2014-04-22 14:44:58 UTC
  • Revision ID: package-import@ubuntu.com-20140422144458-okiwi1assxkkiz39
Tags: upstream-13.09pl1.2+dfsg
Import upstream version 13.09pl1.2+dfsg

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contrib/tsa/libsrc/riembi.for
 
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c
 
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      real function riembi(p,q,x)
 
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c implementation of Lentz's continued fraction 
 
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c based on ideas from Numerical Recipes (Press et. al., 1986)
 
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      implicit none
 
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      real p,q,x,gamlog,rbfrac,zero,one,two,sav
 
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      parameter (zero=0.,one=1.,two=2.)
 
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c Abramovitz & Stegun 1971 (26.5.8)
 
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      if (x.lt.zero.or.x.gt.one) then
 
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cc obsolete Fortran statement: PAUSE
 
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cc        pause 'riembi: argument X out of range'
 
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        riembi = -999999.
 
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        return
 
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      elseif (x.eq.zero.or.x.eq.one) then
 
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        sav=zero
 
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      else
 
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c Abramovitz & Stegun 1971 (6.2.2)
 
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        sav=exp(gamlog(p+q)
 
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     $-gamlog(p)-gamlog(q)+p*log(x)+q*log(one-x))
 
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      endif
 
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c Abramovitz & Stegun 1971 (26.5.8)
 
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      if ((p+one)/(p+q+two).gt.x) then
 
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        riembi=sav*rbfrac(p,q,x)/p
 
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      else
 
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c Abramovitz & Stegun 1971 (26.5.2)
 
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        riembi=one-sav*rbfrac(q,p,one-x)/q
 
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      endif
 
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      end
 
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c
 
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c                                   
 
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c