Quaternion Function Reference

ispure

Test for pure quaternion

Syntax

Y = ispure(X)

Description

ispure(X) returns logical 1 (true) if the quaternion array X is pure.

Mathematically, a pure quaternion has zero scalar part. Here, pure quaternions are stored without a scalar part, and it is the existence of the scalar part which is tested by this function, not its value. Thus a quaternion with a scalar part with value zero is not pure according to the definition used by this function. Similarly, empty quaternions do not have a scalar part (or any part) and therefore this function regards them as pure.

The reason for implementing pure quaternions in the way described is for efficiency: reduced storage, and reduced computation, since computation with pure quaternions can be done without wasting time computing with the zero scalar part.

© 2008-2013 Stephen J. Sangwine and Nicolas Le Bihan

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