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AST_UNITNORMMAP
Create a UnitNormMap
Description:
This function creates a new
UnitNormMap and optionally initialises its attributes.
The forward transformation of a UnitNormMap subtracts the specified centre and then transforms the
resulting vector to a unit vector and the vector norm. The output contains one more coordinate than
the input: the initial Nin outputs are in the same order as the input; the final output is the
norm.
The inverse transformation of a UnitNormMap multiplies each component of the provided vector by
the provided norm and adds the specified centre. The output contains one fewer coordinate than
the input: the initial Nin inputs are in the same order as the output; the final input is the
norm.
UnitNormMap enables radially symmetric transformations, as follows:
-
apply a UnitNormMap to produce a unit vector and norm (radius)
-
apply a one-dimensional mapping to the norm (radius), while passing the unit vector unchanged
-
apply the same UnitNormMap in the inverse direction to produce the result
Invocation
RESULT =
AST_UNITNORMMAP( NCOORD, CENTRE, OPTIONS, STATUS )
Arguments
NCOORD = INTEGER
(Given)
The number of coordinate values for each point to be transformed (i.e. the number of
dimensions of the space in which the points will reside). Output will include one additional
coordinate.
CENTRE( NCOORD ) = DOUBLE PRECISION (Given)
An array containing
the values to be subtracted from the input coordinates before computing unit vector and
norm. A separate value must be supplied for each coordinate.
OPTIONS = CHARACTER
(
)
(Given)
A character string containing an optional comma-separated list of attribute assignments to be
used for initialising the new UnitNormMap. The syntax used is identical to that for the
AST_SET
routine.
STATUS = INTEGER (Given and Returned)
The global status.
Returned Value
AST_UNITNORMMAP = INTEGER
A pointer to the new UnitNormMap.
Notes:
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"
.
Copyright (C) 2014 Science & Technology Facilities Council
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A Library for Handling
World
Coordinate Systems
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