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slalib/imxv.f

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+      SUBROUTINE sla_IMXV (RM, VA, VB)
+*+
+*     - - - - -
+*      I M X V
+*     - - - - -
+*
+*  Performs the 3-D backward unitary transformation:
+*
+*     vector VB = (inverse of matrix RM) * vector VA
+*
+*  (single precision)
+*
+*  (n.b.  the matrix must be unitary, as this routine assumes that
+*   the inverse and transpose are identical)
+*
+*  Given:
+*     RM       real(3,3)    matrix
+*     VA       real(3)      vector
+*
+*  Returned:
+*     VB       real(3)      result vector
+*
+*  P.T.Wallace   Starlink   November 1984
+*
+*  Copyright (C) 1995 Rutherford Appleton Laboratory
+*
+*  License:
+*    This program is free software; you can redistribute it and/or modify
+*    it under the terms of the GNU General Public License as published by
+*    the Free Software Foundation; either version 2 of the License, or
+*    (at your option) any later version.
+*
+*    This program is distributed in the hope that it will be useful,
+*    but WITHOUT ANY WARRANTY; without even the implied warranty of
+*    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+*    GNU General Public License for more details.
+*
+*    You should have received a copy of the GNU General Public License
+*    along with this program (see SLA_CONDITIONS); if not, write to the 
+*    Free Software Foundation, Inc., 59 Temple Place, Suite 330, 
+*    Boston, MA  02111-1307  USA
+*
+*-
+
+      IMPLICIT NONE
+
+      REAL RM(3,3),VA(3),VB(3)
+
+      INTEGER I,J
+      REAL W,VW(3)
+
+
+
+*  Inverse of matrix RM * vector VA -> vector VW
+      DO J=1,3
+         W=0.0
+         DO I=1,3
+            W=W+RM(I,J)*VA(I)
+         END DO
+         VW(J)=W
+      END DO
+
+*  Vector VW -> vector VB
+      DO J=1,3
+         VB(J)=VW(J)
+      END DO
+
+      END