PDF/spdf/afratin.F

   1 *
   2 * $Id$
   3 *
   4 * $Log$
   5 * Revision 1.1.1.2  1996/10/30 08:27:34  cernlib
   6 * Version 7.04
   7 *
   8 * Revision 1.1.1.1  1996/04/12 15:29:01  plothow
   9 * Version 7.01
  10 *
  11 *
  12 #include "pdf/pilot.h"
  13       SUBROUTINE AFRATIN(XA,YA,N,X,Y,DY)
  14       PARAMETER (NMAX=10,TINY=1.E-25)
  15       DIMENSION XA(NMAX),YA(NMAX),C(NMAX),D(NMAX)
  16       Y=0.
  17       IF(N.GT.NMAX) RETURN
  18       NS=1
  19       HH=ABS(X-XA(1))
  20       DO 11 I=1,N
  21         H=ABS(X-XA(I))
  22         IF (H.EQ.0.)THEN
  23           Y=YA(I)
  24           DY=0.0
  25           RETURN
  26         ELSE IF (H.LT.HH) THEN
  27           NS=I
  28           HH=H
  29         ENDIF
  30         C(I)=YA(I)
  31         D(I)=YA(I)+TINY
  32 11    CONTINUE
  33       Y=YA(NS)
  34       NS=NS-1
  35       DO 13 M=1,N-1
  36         DO 12 I=1,N-M
  37           W=C(I+1)-D(I)
  38           H=XA(I+M)-X
  39           T=(XA(I)-X)*D(I)/H
  40           DD=T-C(I+1)
  41 C         IF(DD.EQ.0.)PAUSE
  42           DD=W/DD
  43           D(I)=C(I+1)*DD
  44           C(I)=T*DD
  45 12      CONTINUE
  46         IF (2*NS.LT.N-M)THEN
  47           DY=C(NS+1)
  48         ELSE
  49           DY=D(NS)
  50           NS=NS-1
  51         ENDIF
  52         Y=Y+DY
  53 13    CONTINUE
  54       RETURN
  55       END