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Index Page unormg_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

       unormg_c ( Unit vector and norm, general dimension )

       void unormg_c ( ConstSpiceDouble    v1     [],
                       SpiceInt            ndim,
                       SpiceDouble         vout   [],
                       SpiceDouble       * vmag    )

#### Abstract

       Normalize a double precision vector of arbitrary dimension and
       return its magnitude.

#### 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 v1 / ||v1||.
       vmag       O   Magnitude of `v1', i.e. ||v1||.

#### Detailed_Input

       v1          is an arbitrary double precision n-dimensional vector,
                   including the zero vector.

       ndim        is the dimension of `v1' and `vout'.

#### Detailed_Output

       vout        is the double precision n-dimensional 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

       unormg_c references a function called vnormg_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. No error detection or correction is
       implemented.

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

          Example code begins here.

          /.
             Program unormg_ex1
          ./
          #include <stdio.h>
          #include "SpiceUsr.h"

          int main( )
          {

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

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

             SpiceInt             i;

             /.
             Define the vector set.
             ./
             SpiceDouble          v1     [SETSIZ][NDIM] = {
                                       { 5.0,   12.0,   0.0,   4.0 },
                                       { 1.e-6,  2.e-6, 2.e-6, 0.0 } };

             /.
             Calculate the unit vectors and magnitudes.
             ./
             for ( i = 0; i < SETSIZ; i++ )
             {
                unormg_c ( v1[i], NDIM, vout, &vmag );

                printf( "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( "Magnitude  : %11.7f\n", vmag );
                printf( "\n" );
             }

             return ( 0 );
          }

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

          Vector     :   5.0000000  12.0000000   0.0000000   4.0000000
          Unit vector:   0.3676073   0.8822575   0.0000000   0.2940858
          Magnitude  :  13.6014705

          Vector     :   0.0000010   0.0000020   0.0000020   0.0000000
          Unit vector:   0.3333333   0.6666667   0.6666667   0.0000000
          Magnitude  :   0.0000030

#### Restrictions

       1)  No error checking is implemented in this function to guard
           against numeric overflow.

#### Literature_References

       None.

#### Author_and_Institution

       N.J. Bachman        (JPL)
       J. Diaz del Rio     (ODC Space)
       E.D. Wright         (JPL)

#### Version

       -CSPICE Version 1.3.0, 05-JUL-2021 (JDR)

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

           Updated wrapper to call f2c'ed SPICELIB version.

       -CSPICE Version 1.2.0, 06-FEB-2017 (EDW)

           Bug fix: eliminated spurious semi-colon on "for(...)" line.
           This caused the output vector not to be set when the input
           argument `v1' was the zero vector.

           Corrected section order.

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

           Made input vector const. Converted check-in style to discovery.

       -CSPICE Version 1.0.0, 31-MAR-1998 (EDW)

#### Index_Entries

       n-dimensional unit vector and norm

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

    Fri Dec 31 18:41:14 2021