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Index Page unorm_c

Table of contents

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

       unorm_c ( Unit vector and norm, 3 dimensional )

       void unorm_c ( ConstSpiceDouble     v1[3],
                      SpiceDouble          vout[3],
                      SpiceDouble        * vmag    )

#### Abstract

       Normalize a double precision 3-vector and return its magnitude.

#### Required_Reading

       None.

#### Keywords

       VECTOR

#### Brief_I/O

       VARIABLE  I/O  DESCRIPTION
       --------  ---  --------------------------------------------------
       v1         I     Vector to be normalized.
       vout       O     Unit vector v1 / |v1|.
       vmag       O     Magnitude of v1, i.e. |v1|.

#### Detailed_Input

       v1          is an arbitrary 3-vector, including the
                   zero vector.

#### Detailed_Output

       vout        is the unit vector in the direction  of `v1'. If `v1' is
                   the zero vector, then `vout' will also be the zero
                   vector.

       vmag        is the magnitude of `v1'.

#### Parameters

       None.

#### Exceptions

       Error free.

#### Files

       None.

#### Particulars

       unorm_c references a function called vnorm_c (which itself is
       numerically stable) to calculate the norm of the input vector `v1'.
       If the norm is equal to zero, then each component of the output
       vector `vout' is set to zero. Otherwise, `vout' is calculated by
       dividing `v1' by the norm.

#### 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 and magnitude.

          Example code begins here.

          /.
             Program unorm_ex1
          ./
          #include <stdio.h>
          #include "SpiceUsr.h"

          int main( )
          {

             /.
             Local parameters.
             ./
             #define SETSIZ       2

             /.
             Local variables.
             ./
             SpiceDouble          vmag;
             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 and magnitudes.
             ./
             for ( i = 0; i < SETSIZ; i++ )
             {

                unorm_c ( seta[i], vout, &vmag );

                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( "Magnitude  :  %12.8f\n", vmag );
                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
          Magnitude  :   13.00000000

          Vector     :    0.00000010   0.00000020   0.00000020
          Unit vector:    0.33333333   0.66666667   0.66666667
          Magnitude  :    0.00000030

#### Restrictions

       None.

#### 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 1.1.1, 10-AUG-2021 (JDR)

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

           Header sections have been reordered.

       -CSPICE Version 1.1.0, 22-OCT-1998 (NJB)

           Made input vector const.

       -CSPICE Version 1.0.0, 17-OCT-1997 (EDW) (WMO) (WLT)

#### Index_Entries

       3-dimensional unit vector and norm

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

    Fri Dec 31 18:41:14 2021