Plotting RNTuple same as TTree

[rlalik]

With TTree object in a root file, I could do:

tree->Draw("some_leaf", "some cut", "draw opts");

I was frequently using this e.g. in macros to plot histograms from trees.

Is this still possible with RNTuple? I cannot find anything in the documentation.

[Danilo]

Hi Rafal,

Thanks for the post.
RNTuple can be easily analysed with RDataFrame.

ROOT::RDataFrame df("myTree", "myFileName.root");
auto h = df.Filter("some cut").Histo1D("some_leaf");
h->Draw("draw opts");

Cheers,
Danilo

[rlalik]

Thanks for this example.

However I was thinking about situation where ones open the root file with root. With TTree in the file, you see the tree object and can call obj->Draw(...) directly. Would it be possible to make it the same for RNTuples? Your example is a different approach.

I am thinking about migrating from TTree to RNTuple but lack of RNTuple::Draw means I need to rewrite all the macros we used for our tools set.

I have plenty of macros which I call: root file_name.root macro.C and the macro expects the tree object being available and draw from it.

[pcanal]

Note that to ease the transition you can create a RDataFrame from a TTree (derefenced) pointer.

[Danilo]

Hi Rafał,

Thanks for describing your “user story”, which I find very reasonable and sound.

Let me first observe that the snipped above works if myTree is a TTree or an RNTuple instance - exactly the same code, the input format can be transparently switched.

We consciously decided not to try to re-implement TTree::Draw for RNtuple because of the design of the two columnar formats interfaces, which are intrinsically different. Honestly, it would not be possible to re-implement the entire “TTree::Draw cut language” functionality for RNTuple.

Can we help you somehow with the migration to RDF?

Cheers,
D

[rlalik]

This is very bad. The TTree::Draw() is very handy for quick tree inspection. Like open file in the T/Web browser and with one-liner you can draw almost anything you want. With RDataFrame it becomes convoluted.

So I already see that I will have hard time convincing people to move to RNTuple, and most likely we will stick with TTrees.