Abstract

   CSPICE_VDISTG returns the double precision value of the distance between
   two double precision N-vectors.

I/O

   Given:

      v1,
      v2       two vectors of arbitrary dimension, the distance between which
               is desired.

               help, v1
                  DOUBLE = Array[N]
               help, v2
                  DOUBLE = Array[N]

   the call:

      vdistg = cspice_vdistg( v1, v2 )

   returns:

      vdistg   the distance between `v1' and `v2'.

               help, vdistg
                  DOUBLE = Scalar

               This is defined as

                  ||  v1 - v2  ||,

               where || x || indicates the Euclidean norm of the vector x.

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 two four-dimensional vectors and calculate the distance
      between them.

      Example code begins here.


      PRO vdistg_ex1

         vec1 = [ 12.3d,    -4.32d,  76.d,   1.87d  ]
         vec2 = [ 23.0423d, -11.99d, -0.10d, -99.1d ]

         print, 'Distance between v1 and v2:', cspice_vdistg( vec1, vec2)

      END


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


      Distance between v1 and v2:       127.12347


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

         norm( vec1 - vec2 )

      The IDL function accepts an arbitrary size N-vectors.

Particulars

   The Euclidean norm of an n-dimensional vector

      (x ,  x , ... , x )
        1    2         n

   is defined as

                                              1/2
            2        2                  2
      (   x    +   x    +  . . .  +   x     ).
           1        2                  n

   This number is the distance of the point (x, y, z) from the
   origin. If n = 3, and `a' and `b' are two vectors whose components
   are

      ( a[0], a[1], a[2] )    and    ( b[0], b[1], b[2] ),

   then the distance between `a' and `b' is the norm of the difference
   a - b, which has components

      (  a(0) - b[0],  a(1) - b[1],  a(2) - b[2]  ).

   A related routine is cspice_vdist, which computes the distance between
   two 3-vectors.

Exceptions

   1)  If any of the input arguments, `v1' or `v2', is undefined, an
       error is signaled by the IDL error handling system.

   2)  If any of the input arguments, `v1' or `v2', is not of the
       expected type, or it does not have the expected dimensions and
       size, an error is signaled by the Icy interface.

   3)  If the input vector arguments `v1' and `v2' do not have the
       same dimension (N), 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 1.0.2, 01-JUN-2021 (JDR)

       Edited the header to comply with NAIF standard. Added
       example's problem statement and reformatted example's output.

       Added -Parameters, -Exceptions, -Files, -Restrictions,
       -Literature_References and -Author_and_Institution 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 1.0.1, 13-JUN-2011 (EDW)

       Edits to comply with NAIF standard for Icy headers.

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

Index_Entries

   distance between n-dimensional vectors