Clear up DDID vs SPECTRAL_WINDOW confusion

[jmoldon]

First, thanks a lot for the new version, this is improving really fast!

I have seen that the -c option does not work for SPWs. I don't see spw/datadescid in the data_mappers dictionary, so I guess it is not implemented. I think colourizing by spw would be really useful for other instruments. Probably also many cases would benefit from colourizing by FIELD.

I don't know if those would be plug-and-play additions, but I leave them here as a suggestion.

[o-smirnov]

That which you seek is already there. You can colour by arbitrary column, so -c FIELD_ID and -c DATA_DESC_ID should work out of the box.

(That does remind me that there is some confusion going on between spw and DDID... at the moment shadeMS treats them as one and the same, which they virtually always are, but don't have to be in principle...)

[jmoldon]

That which you seek is already there. You can colour by arbitrary column

That is even better, thanks! A short mention to that in the argparse help would be useful.

Arg, yes ddid-spw translation, annoying as always. The ddids are in the MS:DATA_DESCRIPTION subtable, with the column SPECTRAL_WINDOW_ID matching the spws. And also the SPWs are described in the MS:SPECTRAL_WINDOWS subtable. It is easy to match both by reading the tables directly. I think casacore has functions to match both, but probably it is not needed.

In any case, I have never actually needed to separate them, but you are right that someone (from far far away in a long long time) may have the problem eventually.

[o-smirnov]

Well, the implication is that all axes (x, y, colour, alpha) have the same variation available to them.

You can even colour by e.g. chunks of channels, -c CHAN --cmin 0 --cmax 64 --cnum 8, and by the value of a visibility column...

[o-smirnov]

Renaming the issue since I think @jmoldon's colouring needs have been met...

But the DDID/SPWID logic needs to be cleaned up.