Can the variables inside the UserInfo object be used inside Draw?

ROOT
1

Hello

I have a tree with a UserInfo object. I can access it and check the values stored within:

root [10] .L MyHeader.cpp++
root[11] MyHeader *emh=(MyHeaderr*) tree->GetUserInfo()->At(0)
root[12] emh->GetAverages()
(unsigned short)256

I would like to use the variables stored inside the UserInfo object inside the Draw command, either as varexp or selection strings.

tree->Draw("emh->GetAverages()")
Error in <TTreeFormula::Compile>:  Bad numerical expression : "emh.GetAverages()"

same problem if I use them in the selection field:

tree->Draw("Energy","emh->GetAverages()==256")

Can the variables inside the GetUserInfo object be used at all inside Draw???
Thanks

2

One possible way:

root[10] .L MyHeader.cpp++
root[11] MyHeader *emh=(MyHeaderr*) tree->GetUserInfo()->At(0)
root[12] int avr = emh->GetAverages()
root[13] tree->Draw(Form("%d",avr))
3

Dear Olivier,

thank you for the answer.

But this solution does not work if I want to use the info stored in UserInfo to make a selection. For instance, the data member Averages (returned by GetAverages) is not recognized inside Draw, even if I can access it in the interactive shell:

root[56] emh->Averages
(unsigned short)256
root[57] emh->Draw(“1”,“emh->Averages==256”)
Error in TTreeFormula::Compile: Bad numerical expression : “emh.Averages”
(Long64_t)(-1)

Then, can I answer the question in the original message “Can the variables inside the GetUserInfo object be used at all inside Draw???” with a “no”

Thank you

4

emh->Averages is a single int in your case. So you can do:

root[56] int avr = emh->Averages
root[57] emh->Draw("1",Form("%d==256",avr))

Note the use of the Form function …

5

Thank you.

I see that we need then always the workaround of evaluating the value of the variable before the actual Draw.

Therefore I will not be able to plot:

tree->Draw(“Energy:emh->Averages”)

and then, I would say that in general one can not use literally in tree::Draw the variables stored inside UserInfo. Therefore, if you need to plot/make selections in these variables, it is best to store them as leaves of a branch, despite the fact that they may not change inside the file (but they can change between different files, so one can see that change when chaining files).