Support for TProfile and TProfile2D projectionX and projectionXY options in JSROOT

[will-cern]

Feature description

The projection methods of profile plots (TProfile::ProjectionX and TProfile2D::ProjectionXY) have a bunch of useful options that allow us to visualize useful features like the RMS in each bin, or the sum of weights, or the number of entries in each bin.

I would like to propose that a new context submenu be added to JSROOT for profile plots, or at least a lot more options appear under the "proj" submenu for these plot types. All the different options from these two methods should be available (the options are the same between TProfile and TProfile2D). I actually dont know what the existing options under the "proj" submenu even do, to be honest?

Alternatives considered

No response

Additional context

No response

[linev]

Different kinds of projections are implemented for JSROOT. Like:

http://root.cern/js/latest/examples.htm#th2_projx1
http://root.cern/js/latest/examples.htm#th2_projy3
http://root.cern/js/latest/examples.htm#th2_projxy

It is functionality which is similar to TH2::SetShowProjectionX() / TH2::SetShowProjectionY() / TH2::SetShowProjectionXY().

In principle, it also works with TProfile2D.

That kind of functionality you are missing?

[will-cern]

For example, we are missing the functionality that would show the following histogram:

profile2d->GetProjectionXY("_pxy",OPT)->Draw(DRAWOPT)

Where OPT and DRAWOPT are somehow to be determined. OPT can be one of:

""
"W"
"C=E"
"E"
"B"

[linev]

Do I understand you correctly - you want to have new TProfile2D::ProjectionXY() method with different options which content will be in produced histogram? And also special implementation for TProfile2D::ProjectX() and TProfile2D::ProjectY()? And then display it with custom draw options?

Main question - do you want to have such projections only for visualization or it make sense implementing them in TProfile2D class of ROOT. If only visualization is interesting - one can provide pure JavaScript implementation.

If methods have to be implemented in C++ classes - probably this should be done first and then TWebCanvas/JSROOT can provide support of such methods.

[will-cern]

The use case is that in ATLAS experiment we use JSROOT for display of detector monitoring plots, which include things like efficiency plots that exist as TProfile or TProfile2D. It would be nice to have a way in JSROOT to view the denominator distribution for such a plot, which is obtained from the ProjectionX or ProjectionXY method with the "B" option.

I think this is about visualization in JSROOT. If we had a C++ or python prompt we know what we need to do to view the projection. I just want to have a way to do that just with a JSROOT draw option

[linev]

Now I found TProfile2D::ProjectionXY method. You want to have it implemented in JSROOT.

I need to think how graphically implement it.
Probably show projection on the left side from original histogram?

[will-cern]

Since it's a 2d projection, I would have said you could either view it side-by-side with the original, or you could just this as a different draw option that's unique to tprofile2d. I was imagining the latter, where I see you have the "proj" submenu already, and I would have added options there for each of the options of "projectionxy". And similarly for TProfile::ProjectionX.

But then there is the question of how you would control the option that THAT histogram displays with. Here I can see the benefit of what you propose that it displays the "projection" side-by-side with the original plot. Then you can use the context menu of the projection to change the draw style of it.

[linev]

I implement several new draw options for TProfile2D: projxyb, projxyc=e, projxyw

Example: https://jsroot.gsi.de/dev/examples.htm#tprofile2d_projxyb

I only skipped option 'e' while it makes no big sense - error just remain as is.

JSROOT does not modify histogram but just manipulates internally GetBinContent() method.
Therefore draw options can be switched any time to something else.

Same kind of projection I will provide for TProfile class later.

[will-cern]

Many thanks, this looks super helpful for us because it will save us having to save the bin entries as a separate histogram for our monitoring framework (which displays monitoring plots with JSROOT).
When you add the feature for TProfile, it would be good if at the same time you could do something similar for TEfficiency, to allow display of the "Total histogram" (equivalent to a projection with option "B" in a TProfile that has been used for efficiency), since some of our plots are TEfficiency rather than TProfile.

[linev]

I add projx for TProfile

https://jsroot.gsi.de/dev/examples.htm#tprofile_projxb
https://jsroot.gsi.de/dev/examples.htm#tprofile_projxc=e
https://jsroot.gsi.de/dev/examples.htm#tprofile_projxw

and special 'b' draw option for TEfficiency. String after 'b' used as draw option for total histogram:

https://jsroot.gsi.de/dev/examples.htm#tefficiency_b
https://jsroot.gsi.de/dev/examples.htm#tefficiency_bbox

[will-cern]

Thank you! For the TEfficiency, is it possible to add that draw option to the context menu of the TEfficiency? I note at the moment there is in fact no context menu for TEfficiency (if I select it from the list of drawn primitives, no menu is displayed). Adding a way to switch between the different draw options of TEfficiency through such a context menu is what we ultimately would prefer. Is that possible to do?
Thanks!