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Version 1.9 Build 1488

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coordsys.referencevalue - Function

	Package	general
	Module	images
	Tool	coordsys

Recover the reference value

Synopsis
referencevalue(format, type)

Arguments

format	in	Format string
		Allowed:	String from combination of "n", "q", "s", "m"
		Default:	'n'
type	in	Coordinate type
		Allowed:	String from "direction", "stokes", "spectral", "linear", "tabular" or unset
		Default:	All

Returns
Vector of doubles, vector of quantities, vector of string, record or fail

Description

Each axis associated with the Coordinate System has a reference value, reference pixel and an increment (per pixel). These are used in the mapping from pixel to world coordinate.

This function (short-hand name rv) returns the reference value (in world axis order). You can recover the reference value either for all coordinates (leave type unset) or for a specific coordinate type (mimumum match of the allowed types will do). If you ask for a non-existent coordinate an exception is generated.

See the discussion regarding the formatting possibilities available via argument format.

You can set the reference value with function setreferencevalue.

Example

- cs := coordsys(direction=T, spectral=T)
- cs.referencevalue(format='q')
[__*0=[value=0, unit='], __*1=[value=0, unit='], __*2=[value=1.415e+09, unit=Hz]] 
-
- cs.referencevalue(format='n')
[0 0 1.415e+09]  
-
- cs.referencevalue(format='n', type='spec')
1.415e+09