Table of contents
CSPICE_UNORMG normalizes a double precision vector of arbitrary dimension
and returns its magnitude.
Given:
v1 an arbitrary double precision n-dimensional vector, including
the zero vector.
help, v1
DOUBLE = Array[N]
the call:
cspice_unormg, v1, vout, vmag
returns:
vout the double precision n-dimensional unit vector in the direction
of `v1'.
help, vout
DOUBLE = Array[N]
If `v1' is the zero vector, then `vout' will also be the zero
vector.
vmag the magnitude of `v1'.
help, vmag
DOUBLE = Scalar
None.
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 set of n-dimensional vectors and compute their
corresponding unit vectors and magnitudes.
Example code begins here.
PRO unormg_ex1
;;
;; Local parameters.
;;
SETSIZ = 2L
;;
;; Define the vector set.
;;
v1 = [ [ 5.D0, 12.D0, 0.D0, 4.D0 ], $
[ 1.D-6, 2.D-6, 2.D-6, 0.D0 ] ]
;;
;; Calculate the unit vectors and magnitudes.
;;
for i=0L, SETSIZ-1L do begin
cspice_unormg, v1[*,i], vout, vmag
print, format='(A,4F12.7)', 'Vector :', v1[*,i]
print, format='(A,4F12.7)', 'Unit vector:', vout
print, format='(A,F12.7)', 'Magnitude :', vmag
print
endfor
END
When this program was executed on a Mac/Intel/IDL8.x/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
cspice_unormg references a function called cspice_vnormg (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.
IDL native code to perform the same operation:
vmag = norm(v1)
vout = v1/vmag
The native IDL functions also accept arbitrary sized vectors.
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.
3) If any of the output arguments, `vout' or `vmag', is not a
named variable, an error is signaled by the Icy interface.
None.
1) No error checking is implemented in this routine to guard
against numeric overflow.
ICY.REQ
None.
J. Diaz del Rio (ODC Space)
E.D. Wright (JPL)
-Icy Version 1.0.2, 27-AUG-2021 (JDR)
Edited the header to comply with NAIF standard. Added complete
code examples.
Added -Parameters, -Exceptions, -Files, -Restrictions,
-Literature_References and -Author_and_Institution sections, and
completed -Particulars section.
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, 09-DEC-2005 (EDW)
Added -Examples section.
-Icy Version 1.0.0, 16-JUN-2003 (EDW)
n-dimensional unit vector and norm
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