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  • Committer: useakat at gmail
  • Date: 2012-10-01 07:45:50 UTC
  • mfrom: (4.1.13 gg_3g_cfmc_dev)
  • Revision ID: useakat@gmail.com-20121001074550-zs09eu30khm4yvyx
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library/gmline.f
 
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*   15/05/85 508092014 MEMBER NAME  GMLINE   (S)           FORTRAN
 
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************************************************************************
 
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*     ---------------------------------------
 
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      SUBROUTINE GMLINE(X1,Y1,X2,Y2,A,B,IERR)
 
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*     ---------------------------------------
 
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*
 
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*     (Purpose)
 
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*        Calculate a gradient and a intercept of line
 
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*        when two points are given.
 
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*
 
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*     (Input)
 
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*        X1,Y1  : coordinate of one point.
 
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*        X2,Y2  : coordinate of another point.
 
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*
 
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*     (Output)
 
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*        A        : a gradient of the line
 
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*        B        : a intercept of the line
 
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*        IERR = 0 : Normal end
 
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*             = 1 : No solution is found.
 
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*
 
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************************************************************************
 
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      REAL*8 DX1,DY1,DX2,DY2
 
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      REAL*8 DA,DB
 
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      IF(X1.EQ.X2) THEN
 
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         IERR=1
 
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         A=0.
 
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         B=0.
 
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      ELSE
 
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         IERR=0
 
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         DX1=X1
 
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         DY1=Y1
 
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         DX2=X2
 
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         DY2=Y2
 
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         DA=(DY1-DY2)/(DX1-DX2)
 
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         DB=DY1-DA*DX1
 
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         A=DA
 
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         B=DB
 
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      END IF
 
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      RETURN
 
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      END