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IsLinear - Is the Mapping linear?

Description:
This attribute indicates whether a Mapping is an instance of a class that always represents a linear transformation. Note, some Mapping classes can represent linear or non-linear transformations (the MathMap class for instance). Such classes have a zero value for the IsLinear attribute. Specific instances of such classes can be tested for linearity using the astLinearApprox function. AST_LINEARAPPROX routine.
Type:
Integer (boolean), read-only.
Class Applicability:
Mapping
All Mappings have this attribute.
CmpMap
The IsLinear value for a CmpMap is determined by the classes of the encapsulated Mappings. For instance, a CmpMap that combines a ZoomMap and a ShiftMap will have a non-zero value for its IsLinear attribute, but a CmpMap that contains a MathMap will have a value of zero for its IsLinear attribute.
Frame
The IsLinear value for a Frame is 1 (since a Frame is equivalent to a UnitMap).
FrameSet
The IsLinear value for a FrameSet is obtained from the Mapping from the base Frame to the current Frame.


next up previous 264
Next: IsLonAxis(axis) - Is the specified celestial axis a longitude axis?
Up: AST Attribute Descriptions
Previous: IsLatAxis(axis) - Is the specified celestial axis a latitude axis?

AST A Library for Handling World Coordinate Systems in Astronomy
Starlink User Note 211
R.F. Warren-Smith & D.S. Berry
7th December 2012
E-mail:starlink@jiscmail.ac.uk

Copyright (C) 2012 Science \& Technology Facilities Council