coordsys.restfrequency

Recover the rest frequency

Synopsis
restfrequency()

Returns
Quantity or fail

Description

If the Coordinate System contains a spectral coordinate, then it has a rest frequency. In fact, the spectral coordinate can hold several rest frequencies (to handle for example, an observation where the band covers many lines), although only one is active (for velocity conversions) at a time.

This function (short-hand name rf) recovers the rest frequencies as a quantity vector. The first frequency is the active one.

You can change the rest frequencies with setrestfrequency.

If the Coordinate System does not contain a frequency coordinate, an exception is generated.

Example

- cs := coordsys(spectral=T)
- cs.restfrequency()
[value=1.42040575e+09, unit=Hz] 
-
- cs.setrestfrequency (value=[1.2e9. 1.3e9], which=2, append=F)
- cs.restfrequency()
[value=[1.3e+09 1.2e+09] , unit=Hz]

In the example, the initial spectral coordinate has 1 rest frequency. Then we set it with two, nominating the second as the active rest frequency, and recover them.

Next: coordsys.setconversiontype - Function Up: coordsys - Tool Previous: coordsys.replace - Function Contents Index

	Package	general
	Module	images
	Tool	coordsys

coordsys.restfrequency - Function