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astNormMap - Create a NormMap

Description:
This function creates a new NormMap and optionally initialises its attributes.

A NormMap is a Mapping which normalises coordinate values using the astNorm function of the supplied Frame. The number of inputs and outputs of a NormMap are both equal to the number of axes in the supplied Frame.

The forward and inverse transformation of a NormMap are both defined but are identical (that is, they do not form a real inverse pair in that the inverse transformation does not undo the normalisation, instead it reapplies it). However, the astSimplify function will replace neighbouring pairs of forward and inverse NormMaps by a single UnitMap.

Synopsis:
AstNormMap $*$astNormMap( AstFrame $*$frame, const char $*$options, ... )
Parameters:
frame
A pointer to the Frame which is to be used to normalise the supplied axis values.
options
Pointer to a null-terminated string containing an optional comma-separated list of attribute assignments to be used for initialising the new NormMap. The syntax used is identical to that for the astSet function and may include "printf" format specifiers identified by "%" symbols in the normal way.
...
If the "options" string contains "%" format specifiers, then an optional list of additional arguments may follow it in order to supply values to be substituted for these specifiers. The rules for supplying these are identical to those for the astSet function (and for the C "printf" function).
Returned Value:
astNormMap()
A pointer to the new NormMap.
Notes:
  • A null Object pointer (AST__NULL) will be returned if this function is invoked with the AST error status set, or if it should fail for any reason.
Status Handling
The protected interface to this function includes an extra parameter at the end of the parameter list descirbed above. This parameter is a pointer to the integer inherited status variable: "int $*$status".


next up previous 264
Next: astNullRegion - Create a NullRegion
Up: AST Function Descriptions
Previous: astNorm - Normalise a set of Frame coordinates

AST A Library for Handling World Coordinate Systems in Astronomy
Starlink User Note 211
R.F. Warren-Smith & D.S. Berry
24th May 2011
E-mail:ussc@star.rl.ac.uk

Copyright (C) 2009 Science \& Technology Facilities Council