* SUBROUTINE MXVROT               ALL SYSTEMS                91/12/01
* PORTABILITY : ALL SYSTEMS
* 91/12/01 LU : ORIGINAL VERSION
*
* PURPOSE :
* PLANE ROTATION IS APPLIED TO TWO VALUES.
*
* PARAMETERS :
*  RU  XK  FIRST VALUE FOR PLANE ROTATION.
*  RU  XL  SECOND VALUE FOR PLANE ROTATION.
*  RI  CK  DIAGONAL ELEMENT OF THE ELEMENTARY ORTHOGONAL MATRIX.
*  RI  CL  OFF-DIAGONAL ELEMENT OF THE ELEMENTARY ORTHOGONAL MATRIX.
*  II  IER  INFORMATION ON THE TRANSFORMATION. IER=0-GENERAL PLANE
*         ROTATION. IER=1-PERMUTATION. IER=2-TRANSFORMATION SUPPRESSED.
*
      SUBROUTINE MXVROT(XK,XL,CK,CL,IER)
      DOUBLE PRECISION CK,CL,XK,XL
      INTEGER          IER
      DOUBLE PRECISION YK,YL
      IF (IER.EQ.0) THEN
          YK = XK
          YL = XL
          XK = CK*YK + CL*YL
          XL = CL*YK - CK*YL
      ELSE IF (IER.EQ.1) THEN
          YK = XK
          XK = XL
          XL = YK
      END IF
      RETURN
      END