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Index Page vhat_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

       vhat_c ( "V-Hat", unit vector along V, 3 dimensions )

       void vhat_c ( ConstSpiceDouble  v1  [3],
                     SpiceDouble       vout[3] )

#### Abstract

       Find the unit vector along a double precision 3-dimensional vector.

#### Required_Reading

       None.

#### Keywords

       VECTOR

#### Brief_I/O

       VARIABLE  I/O  DESCRIPTION
       --------  ---  --------------------------------------------------
       v1         I   Vector to be unitized.
       vout       O   Unit vector v1 / |v1|.

#### Detailed_Input

       v1          is any double precision, 3-dimensional vector.

#### Detailed_Output

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

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

#### Parameters

       None.

#### Exceptions

       Error free.

       1)  If `v1' represents the zero vector, then `vout' will also be the
           zero vector.

#### Files

       None.

#### Particulars

       vhat_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 3-dimensional vectors.

#### 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 vectors and compute their corresponding unit
          vector.

          Example code begins here.

          /.
             Program vhat_ex1
          ./
          #include <stdio.h>
          #include "SpiceUsr.h"

          int main( )
          {

             /.
             Local parameters.
             ./
             #define SETSIZ       2

             /.
             Local variables.
             ./
             SpiceDouble          vout   [3];

             SpiceInt             i;

             /.
             Define the vector set.
             ./
             SpiceDouble          seta   [SETSIZ][3] = {
                                       {5.0,  12.0,  0.0},
                                       {1.e-7,  2.e-7, 2.e-7} };

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

                vhat_c ( seta[i], vout );

                printf( "Vector     :  %12.8f %12.8f %12.8f\n",
                             seta[i][0], seta[i][1], seta[i][2] );
                printf( "Unit vector:  %12.8f %12.8f %12.8f\n",
                                      vout[0], vout[1], vout[2] );
                printf( " \n" );

             }

             return ( 0 );
          }

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

          Vector     :    5.00000000  12.00000000   0.00000000
          Unit vector:    0.38461538   0.92307692   0.00000000

          Vector     :    0.00000010   0.00000020   0.00000020
          Unit vector:    0.33333333   0.66666667   0.66666667

#### Restrictions

       1)  There is no known case whereby floating point overflow may
           occur. Thus, no error recovery or reporting scheme is
           incorporated into this routine.

#### Literature_References

       None.

#### Author_and_Institution

       N.J. Bachman        (JPL)
       J. Diaz del Rio     (ODC Space)
       W.M. Owen           (JPL)
       W.L. Taber          (JPL)
       E.D. Wright         (JPL)

#### Version

       -CSPICE Version 1.0.3, 10-AUG-2021 (JDR)

           Edited the header to comply with NAIF standard. Added
           complete code example to -Examples section.

       -CSPICE Version 1.0.2, 16-JAN-2008 (EDW)

           Corrected typos in header titles:

           Detailed Input to -Detailed_Input
           Detailed Output to -Detailed_Output

       -CSPICE Version 1.0.1, 12-NOV-2006 (EDW)

           Added -Parameters section header.

       -CSPICE Version 1.0.0, 16-APR-1999 (EDW) (WMO) (WLT) (NJB)

#### Index_Entries

       unitize a 3-dimensional vector

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

    Fri Dec 31 18:41:14 2021