mtxm_c

Index Page mtxm_c
A B C D E F G H I J K L M N O P Q R S T U V W X
Procedure Abstract Required_Reading Keywords Brief_I/O Detailed_Input | Detailed_Output Parameters Exceptions Files Particulars Examples | Restrictions Literature_References Author_and_Institution Version Index_Entries
#### Procedure
       void mtxm_c ( ConstSpiceDouble    m1  [3][3],
                     ConstSpiceDouble    m2  [3][3],
                     SpiceDouble         mout[3][3] )
#### Abstract
       Multiply the transpose of a 3x3 matrix and a 3x3 matrix.
#### Required_Reading
       None.
#### Keywords
       MATRIX
#### Brief_I/O
       VARIABLE  I/O  DESCRIPTION
       --------  ---  --------------------------------------------------
       m1         I   3x3 double precision matrix.
       m2         I   3x3 double precision matrix.
       mout       O   The produce m1 transpose times m2.
#### Detailed_Input
       m1         is any 3x3 double precision matrix. Typically,
                  m1 will be a rotation matrix since then its
                  transpose is its inverse (but this is not a
                  requirement).

       m2         is any 3x3 double precision matrix.
#### Detailed_Output
       mout       is a 3x3 double precision matrix. mout is the
                  product

                              t
                     mout = m1  m2

                  mout may overwrite either m1 or m2.
#### Parameters
       None.
#### Exceptions
       Error free.
#### Files
       None
#### Particulars
       The code reflects precisely the following mathematical expression

       For each value of the subscripts i and j from 0 to 2:

                         2
                        __
                        \
          mout[i][j] =  /_  m1[k][i] * m2[k][j]
                        k=0

       Note that the reversal of the k and i subscripts in the left-hand
       matrix m1 is what makes mout the product of the TRANSPOSE of M1
       and not simply of m1 itself.  Also, the intermediate results of
       the operation above are buffered in a temporary matrix which is
       later moved to the output matrix.  Thus mout can be actually be
       m1 or m2 if desired without interfering with the computations.
#### Examples
       Let m1 = | 1.  2.  3. |
                |            |
                | 4.  5.  6. |
                |            |
                | 7.  8.  9. |

           m2 = |  1.   1.  0. |
                |              |
                | -1.   1.  0. |
                |              |
                |  0.   0.  1. |

       then the call

       mtxm_c ( m1, m2, mout );

       produces the matrix

       mout = | -3.   5.  7. |
              |              |
              | -3.   7.  8. |
              |              |
              | -3.   9.  9. |
#### Restrictions
       The user is responsible for checking the magnitudes of the
       elements of m1 and m2 so that a floating point overflow does
       not occur.  (In the typical use where m1 and m2 are rotation
       matrices, this not a risk at all.)
#### Literature_References
       None.
#### Author_and_Institution
       W.M. Owen       (JPL)
       E.D  Wright     (JPL)
#### Version
       -CSPICE Version 1.0.0, 16-APR-1999 (EDW)
#### Index_Entries
       matrix_transpose times matrix 3x3_case
#### Link to routine mtxm_c source file mtxm_c.c

    Thu Apr 16 08:58:38 2009