[RDF] support bar charts in RDataFrame

[silverweed]

Feature description

It would be nice if RDataFrame supported bar charts (aka TH[123] with alphanumeric bins). Currently there is a way to achieve it with a user-defined helper, but having a native API would be helpful.
Internally the helper should probably use a TH1L to store the count of occurrences for the column.

Alternatives considered

No response

Additional context

This would allow modernizing tutorials such as this and avoid the use of TTree::Draw

[dpiparo]

This is an interesting feature request: thanks. The current formulation seems to hint to the need of it to modernise a tutorial. The cost benefit ratio, as it stands, does not seem too favourable. Would the feature also address an explicit need of ROOT's users?

[silverweed]

@dpiparo the only user case I'm aware of is the forum thread linked above by @will-cern

[Aditya-138-12]

Hello @vepadulano I would love to help on this feature request...

[dpiparo]

Hi @Aditya-138-12 ! Thanks for reaching out. Would you like to try to propose a PR, test coverage and an example of this functionality?

[Aditya-138-12]

Hi, @dpiparo ! yeah sure, working on it!!

[dpiparo]

Hi @Aditya-138-12 did you encounter difficulties?

[Aditya-138-12]

Hi @dpiparo, @vepadulano , @martamaja10
I’ve implemented bar chart functionality for supporting Alphanumeric bins in RDataFrame using a custom class for TH1D. After building ROOT and testing it in the CLI with .L <file_name.h>+, it works well.

Could you kindly guide me on which files to modify to integrate this into ROOT?

Thank you for your time and support!

[Aditya-138-12]

Hi @vepadulano @dpiparo @martamaja10

I wanted to follow up on this. I’ve implemented bar chart functionality for supporting alphanumeric bins in RDataFrame using a custom class for TH1D. After testing it in the CLI with .L <file_name.h>+, it works as expected.

Could you kindly guide me on which files I should modify to integrate this into ROOT? I would really appreciate your insights.

Thank you for your time and support!