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Index Page vhatg_c

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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

       vhatg_c ( "V-Hat", unit vector along V, general dimension )

       void vhatg_c ( ConstSpiceDouble   * v1,
                      SpiceInt             ndim,
                      SpiceDouble        * vout )

#### Abstract

       Find the unit vector along a double precision vector of
       arbitrary dimension.

#### Required_Reading

       None.

#### Keywords

       VECTOR

#### Brief_I/O

       VARIABLE  I/O  DESCRIPTION
       --------  ---  --------------------------------------------------
       v1         I   Vector to be normalized.
       ndim       I   Dimension of `v1' (and also `vout').
       vout       O   Unit vector along `v1'.

#### Detailed_Input

       v1          is any double precision vector of arbitrary dimension.

       ndim        is the dimension of `v1' (and also `vout').

#### Detailed_Output

       vout        is the unit vector in the direction of `v1':

                                v1
                      vout = --------
                              ||v1||

                   If `v1' represents the zero vector, then `vout' will also be
                   the zero vector. `vout' may overwrite `v1'.

#### Parameters

       None.

#### Exceptions

       Error free.

#### Files

       None.

#### Particulars

       vhatg_c determines the magnitude of `v1' and then divides each
       component of `v1' by the magnitude. This process is highly stable
       over the whole range of multi-dimensional vectors.

       This routine will detect if `v1' the zero vector, and will not
       attempt to divide by zero.

#### Examples

       The numerical results shown for this example may differ across
       platforms. The results depend on the SPICE kernels used as
       input, the compiler and supporting libraries, and the machine
       specific arithmetic implementation.

       1) Define a set of n-dimensional vectors and find the unit vector
          along each of them.

          Example code begins here.

          /.
             Program vhatg_ex1
          ./
          #include <stdio.h>
          #include "SpiceUsr.h"

          int main( )
          {

             /.
             Local parameters.
             ./
             #define NDIM         4
             #define SETSIZ       2

             /.
             Local variables.
             ./
             SpiceDouble          vout   [NDIM];

             SpiceInt             i;

             /.
             Define the vector set.
             ./
             SpiceDouble          v1     [SETSIZ][NDIM] = {
                                       { 5.0,    12.0,  0.0,   0.0 },
                                       { 1.e-7,  2.e-7, 2.e-7, 0.0 } };

             /.
             Calculate the unit vectors.
             ./
             for ( i = 0; i < SETSIZ; i++ )
             {

                vhatg_c ( v1[i], NDIM, vout );

                printf( "Input vector:  %11.7f %11.7f %11.7f %11.7f\n",
                                 v1[i][0], v1[i][1], v1[i][2], v1[i][3] );
                printf( "Unit vector :  %11.7f %11.7f %11.7f %11.7f\n",
                                     vout[0], vout[1], vout[2], vout[3] );
                printf( "\n" );

             }

             return ( 0 );
          }

          When this program was executed on a Mac/Intel/cc/64-bit
          platform, the output was:

          Input vector:    5.0000000  12.0000000   0.0000000   0.0000000
          Unit vector :    0.3846154   0.9230769   0.0000000   0.0000000

          Input vector:    0.0000001   0.0000002   0.0000002   0.0000000
          Unit vector :    0.3333333   0.6666667   0.6666667   0.0000000

#### Restrictions

       1)  The relative number of cases whereby floating point overflow
           may occur is negligible. Thus, no error recovery or reporting
           scheme is incorporated into this function.

#### Literature_References

       None.

#### Author_and_Institution

       N.J. Bachman        (JPL)
       J. Diaz del Rio     (ODC Space)
       W.M. Owen           (JPL)

#### Version

       -CSPICE Version 1.0.1, 05-JUL-2021 (JDR)

           Edited the header to comply with NAIF standard. Added complete
           code example based on existing example.

       -CSPICE Version 1.0.0, 13-JUL-1999 (NJB) (WMO)

#### Index_Entries

       unitize a n-dimensional vector

#### Link to routine vhatg_c source file vhatg_c.c

    Fri Dec 31 18:41:14 2021