SUBROUTINE iau_RV2M ( W, R )
*+
* - - - - - - - - -
* i a u _ R V 2 M
* - - - - - - - - -
*
* Form the r-matrix corresponding to a given r-vector.
*
* This routine is part of the International Astronomical Union's
* SOFA (Standards of Fundamental Astronomy) software collection.
*
* Status: vector/matrix support routine.
*
* Given:
* W d(3) rotation vector (Note 1)
*
* Returned:
* R d(3,3) rotation matrix
*
* Notes:
*
* 1) A rotation matrix describes a rotation through some angle about
* some arbitrary axis called the Euler axis. The "rotation vector"
* supplied to this routine has the same direction as the Euler axis,
* and its magnitude is the angle in radians.
*
* 2) If W is null, the indentity matrix is returned.
*
* 3) The reference frame rotates clockwise as seen looking along the
* rotation vector from the origin.
*
* This revision: 2020 August 21
*
* SOFA release 2021-05-12
*
* Copyright (C) 2021 IAU SOFA Board. See notes at end.
*
*-----------------------------------------------------------------------
IMPLICIT NONE
DOUBLE PRECISION W(3), R(3,3)
DOUBLE PRECISION X, Y, Z, PHI, S, C, F
* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
* Euler angle (magnitude of rotation vector) and functions.
X = W(1)
Y = W(2)
Z = W(3)
PHI = SQRT(X*X + Y*Y + Z*Z)
S = SIN(PHI)
C = COS(PHI)
F = 1D0 - C
* Euler axis (direction of rotation vector), perhaps null.
IF ( PHI .GT. 0D0 ) THEN
X = X / PHI
Y = Y / PHI
Z = Z / PHI
END IF
* Form the rotation matrix.
R(1,1) = X*X*F + C
R(1,2) = X*Y*F + Z*S
R(1,3) = X*Z*F - Y*S
R(2,1) = Y*X*F - Z*S
R(2,2) = Y*Y*F + C
R(2,3) = Y*Z*F + X*S
R(3,1) = Z*X*F + Y*S
R(3,2) = Z*Y*F - X*S
R(3,3) = Z*Z*F + C
* Finished.
*+----------------------------------------------------------------------
*
* Copyright (C) 2021
* Standards Of Fundamental Astronomy Board
* of the International Astronomical Union.
*
* =====================
* SOFA Software License
* =====================
*
* NOTICE TO USER:
*
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*
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*
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*
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*
*-----------------------------------------------------------------------
END