Abstract

   CSPICE_VNORMG returns a scalar double describing the vector norm
   of an N vector where the vector norm is defined as the magnitude of
   the vector.

I/O

   Given:

      v1       any double precision vector of arbitrary dimension, whose
               magnitude is to be found.

               help, v1
                  DOUBLE = Array[N]

   the call:

      vnormg = cspice_vnormg( v1 )

   returns:

      vnormg   the magnitude of `v1' calculated in a numerically stable way.

               help, vnormg
                  DOUBLE = Scalar

Parameters

   None.

Examples

   Any numerical results shown for this example may differ between
   platforms as the results depend on the SPICE kernels used as input
   and the machine specific arithmetic implementation.

   1) Define a four-dimensional vector and calculate its magnitude.

      Example code begins here.


      PRO vnormg_ex1

         v1 = [ 12.3d,    -4.32d,  76.d,   1.87d  ]

         print, 'Magnitude of v1:', cspice_vnormg( v1 )

      END


      When this program was executed on a Mac/Intel/IDL8.x/64-bit
      platform, the output was:


      Magnitude of v1:       77.132673


      Note, the native IDL code to calculate the same scalar result:

         vnormg = norm( vec )

      The IDL function accepts an arbitrary size N-vectors.

Particulars

   cspice_vnormg finds the component of `v1' whose magnitude is the largest.
   If the absolute magnitude of that component indicates that a
   numeric overflow would occur when it is squared, or if it
   indicates that an underflow would occur when squared (falsely
   giving a magnitude of zero) then the following expression is
   used:

      cspice_vnormg = v1max * MAGNITUDE OF [ (1/v1max)*v1 ]

   Otherwise a simpler expression is used:

      cspice_vnormg = MAGNITUDE OF [ v1 ]

   Beyond the logic described above, no further checking of the
   validity of the input is performed.

Exceptions

   1)  If the input argument `v1' is undefined, an error is signaled
       by the IDL error handling system.

   2)  If the input argument `v1' is not of the expected type, or it
       does not have the expected dimensions and size, an error is
       signaled by the Icy interface.

Files

   None.

Restrictions

   None.

Required_Reading

   ICY.REQ

Literature_References

   None.

Author_and_Institution

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

Version

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

       Edited the -I/O section to comply with NAIF standard.

       Added -Examples, -Particulars and -Parameters sections.

       Removed reference to the routine's corresponding CSPICE header from
       -Abstract section.

       Added arguments' type and size information in the -I/O section.

   -Icy Version 1.0.2, 23-SEP-2008 (EDW)

       Eliminated error in English.

   -Icy Version 1.0.1, 09-DEC-2005 (EDW)

       Added -Examples section.

   -Icy Version 1.0.0, 16-JUN-2003 (EDW)

Index_Entries

   norm of n-dimensional vector