I’m using TH2F histograms for plotting sky maps in galactic coordinates. The AITOFF option works well.
Unfortunately, galactic coordinates are defined such that the X axis is reversed when sky maps are plotted: typical sky-map plots range from +180 to -180 for X (longitude), and from -90 to +90 for Y (latitude).
To workaround this under root, I am currently filling my TH2Fs after replacing the original X values into -X. After that, of course, I have to hide the resulting X-labels, and re-draw them by hand. It works, but it is a quite artificial procedure.
So… since the above “issue” is known in astronomy, is there any drawing option to automatically show a X-reverse plot??
This in on our to-do list but we have not yet found time and manpower to do it:
Thank you, Couet. I want note that some collaborations (such as Augers) make extensive use of sky-map plots under Root as reference software. It is likely that some tools are already developed and they only need to be properly incorporated in Root.
I would be happy to incorporate a such tool if it exists.
Can you point to one of them ?
[quote=“couet”]I would be happy to incorporate a such tool if it exists.
Can you point to one of them ?[/quote]
Unfortunately not, but a google search gave me this:
What I understand is that there are some algorithms to manually draw the axis grids according to a given projection (Hammer-Aitoff, Sanson-Flamsteed, Parabolic). Something similar is done for their data-points.
From above, I have now extracted some relevant stuff for this example macro:
ams.pg.infn.it/~tomasset/temp/Dr … roject.cpp
Hope it may be useful (not really sure; hmm…).
By the way… If I correctly understand, the AITOFF representation can be plotted only under the “CONT4” option. I confirm the need of other options (like COL) for plotting fine-binned astronomy data. I think this should be easier to implement under Root, and can be implemented independenly on the -X issue.
Yes it is implement that way only right now.
Still no easy way for drawing skymap with reverse axis?
Does TH1D or TH2D support reverse axis?
TCanvas::DrawFrame() return a histogram;
but it seems ‘reverse axis’ is not support?
No. there is thus example but it is a trick not a direct support: