Procedure

   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|.
                    If v1 = 0, vout will also be zero.
                    vout can overwrite v1.
    vmag      O     Magnitude of v1, that is, |v1|.

Detailed_Input

   v1      This variable may contain any vector of arbitrary
           dimension, including the zero vector.
   ndim    This is the dimension of v1 and vout.

Detailed_Output

   vout    This variable contains the unit vector in the direction
           of v1.  If v1 is the zero vector, then vout will also be
           the zero vector.

   vmag    This is the magnitude of v1.

Parameters

   None.

Exceptions

   1)  If ndim is not physically realistic, greater than zero, a
       BADDIMENSION error is flagged.

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 following table shows how selected v1 implies vout and mag.

   v1                    ndim   vout                   mag
   -----------------------------------------------------------------
   (5, 12)               2      (5/13, 12/13)          13
   (1D-7, 2D-7, 2D-7)    3      (1/3, 2/3, 2/3)        3D-7

Restrictions

   No error checking is implemented in this subroutine to guard
   against numeric overflow.

Literature_References

   None.

Author_and_Institution

   W.M. Owen       (JPL)
   W.L. Taber      (JPL)
   E.D. Wright     (JPL)

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