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QTNORMALIZE

QTNORMALIZE

Name


  QTNORMALIZE

Author


  Craig B. Markwardt, NASA/GSFC Code 662, Greenbelt, MD 20770
  craigm@lheamail.gsfc.nasa.gov
  UPDATED VERSIONs can be found on my WEB PAGE:
      http://cow.physics.wisc.edu/~craigm/idl/idl.html

Purpose


  Normalize a quaternion (unit quaternion and/or sign conventions)

Major Topics


  Geometry

Calling Sequence


  QNEW = QTNORMALIZE(QOLD, UNITIZE=1, POS3=1)

Description



  The function QTNORMALIZE performs normalization operations upon a
  quaternion. The two operations are: UNITIZE and POS3.
  The UNITIZE operation occurs if /UNITIZE is set (this is the
  default). If set, then the returned quaternion is a unit
  quaternion. Non-unit input quaternions will be adjusted so that
  the components have the same ratios, but unit magnitude.
  The POS3 operation occurs if /POS3 is set (this is the default).
  If set, then the returned quaternion is ensured to be positive in
  its third component. In other words, QNEW[3] GE 0. Since the
  same quaternion can have two different representations, differing
  only in the signs of the components, the POS3 operation ensures
  that one sign convention is used for all quaternions. This is
  useful for comparing quaternion component values.
  By default /UNITIZE and /POS3 are both set. In order to disable
  them, set UNITIZE=0 or POS3=0 explicitly.

Inputs



  Q - array of one or more unit quaternions. For a single
      quaternion, Q should be a 4-vector. For N quaternions, Q
      should be a 4xN array.

Returns



  The resulting normalized quaternions. For single inputs, returns
  a 4-vector. For N inputs, returns N quaternions as a 4xN array.

Keyword Parameters



  UNITIZE - if set, then perform UNITIZE operation as described
            above. By default, UNITIZE=1.
  POS3 - if set, then perform POS3 operation as described above. By
          default, POS3=1.

Example


See Also


  QTANG, QTAXIS, QTCOMPOSE, QTERP, QTEXP, QTFIND, QTINV, QTLOG,
  QTMAT, QTMULT, QTPOW, QTVROT

Modification History


  Written, 2012-08-01, CM
  $Id: qtnormalize.pro,v 1.2 2012/10/02 12:29:33 cmarkwar Exp $



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