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QTNORMALIZE

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)

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

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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