CSPICE_VDISTG returns the double precision value of the distance between
two double precision Nvectors.
For important details concerning this module's function, please refer to
the CSPICE routine vdistg_c.
Given:
vec1,
vec2 two double precision Nvectors, the distance between
which is desired.
the call:
dist = cspice_vdistg( vec1, vec2 )
returns:
dist double precision scalar distance between 'vec1' and 'vec2'.
This is defined as
 v1  v2 ,
where  x  indicates the Euclidean norm of the vector x.
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.
vec1 = [ 12.3d, 4.32d, 76.d, 1.87d ]
vec2 = [ 23.0423d, 11.99d, 0.10d, 99.1d ]
print, cspice_vdistg( vec1, vec2)
IDL outputs:
127.12347
Native IDL code to calculate the same scalar result:
norm( vec1  vec2 )
The IDL function accepts an arbitrary size Nvectors.
The Euclidean norm of an ndimensional 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 3vectors.
ICY.REQ
Icy Version 1.0.1, 13JUN2011, EDW (JPL)
Edits to comply with NAIF standard for Icy headers.
Icy Version 1.0.0, 16JUN2003, EDW (JPL)
distance between ndimensional vectors
