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coordsys.torelmany - Function

	Package	general
	Module	images
	Tool	coordsys

Convert many numeric absolute coordinates to relative

Synopsis
torelmany(value, isworld)

Arguments

value	in	Absolute coordinates
		Allowed:	Numeric matrix
isworld	in	Is coordinate world or pixel ?
		Allowed:	T, F, unset
		Default:	unset

Returns
Numeric matrix or fail

Description

This function converts many absolute coordinates to relative. It exists so you can efficiently make many conversions (which would be rather slow if you did them all with torel). Because speed is the object, the interface is purely in terms of numeric matrices, rather than being able to accept strings and quanta etc. like torel can.

When dealing with world coordinates, the units of the numeric values must be the native units, given by function units.

Example

- cs := coordsys(direction=T, spectral=T)    # 3 axes
-
- w := cs.referencevalue();                  # reference value
- inc := cs.increment();                     # increment
- idx := 0:99;
- off := inc[3] * idx;                       # offset for third axis
- wabs := array (w, 3, 100);                 # 100 conversions each of length 3
- wabs[3,] +:= off;                          # Make spectral axis values change
-
- wrel  := cs.torelmany (wabs, T)            # Convert
- wrel[,1]                                   # First relative coordinate
[0 0 0]  
- wrel[,100]                                 # 100th relative coordinate
[0 0 99000]

This example uses world coordinates.