Using Vectors in TTree::Draw

ROOT
1

I am using TTrees that have vector<> and vector<vector<>> data members. I am having trouble using them in TTree::Draw().

For example, if I have “vector< vector > *ADC”, how would I use it in a TTree::Draw statement? It is especially confusing because it is a pointer.

I’ve tried the following:

tree->Draw(“ADC[0][2]”,“ADC[][] > 45”);
This seems to work

tree->Draw(“ADC[][2]”,“ADC[0][2] > 45”);
This yields a plot with many entries in the bin from 0 to 1, which doesn’t make sense since there shouldn’t be any none zero ADCs in the tree.

tree->Draw(“ADC[][]”,“ADC[0][2] > 45”);
This seems to work reasonably.

tree->Draw(“ADC[][]”,“ADC[][] > 45”);
This seems to work reasonably.

I’m just not sure what is the supported syntax. Is this discussed anywhere?

Thanks.

2

Hi,

Which version of ROOT are you using?
Can you provide an simple example reproducing this issue?

Cheers,
Philippe.

3

ROOT Version 5.18/00a (lxplus version)

I suppose my question was more of an informational question, not really a problem as of yet.

Can you just confirm the proper syntax for using vectors and vectors of vectors in the strings passed to the TTree::Draw() method? I can’t find any examples anywhere which specifies this.

Thanks.

4

[quote]I suppose my question was more of an informational question, not really a problem as of yet. [/quote]Humm … you did say:[quote]tree->Draw(“ADC[][2]”,“ADC[0][2] > 45”);
This yields a plot with many entries in the bin from 0 to 1, which doesn’t make sense since there shouldn’t be any none zero ADCs in the tree. [/quote]which may or may not be a problem depending on the data …

[quote]Can you just confirm the proper syntax for using vectors and vectors of vectors in the strings passed to the TTree::Draw() method? I can’t find any examples anywhere which specifies this. [/quote]You seem to have gotten the syntax right. The syntax is described in the documentation of TTree::Draw where the vector of vector is simply an instance of the case of a 2 dimensional array with 2 varying length dimensions.

Cheers,
Philippe.

5

After closer inspection, this seems to work in all of the previously discussed situations.

But it is good to hear that this is the correct syntax. Thank you.

6

Now I think I have encountered a problem.

Again, I am using a “vector<vector>* ADC” where the inner vector has 5 entries always.

TTree::Draw("(ADC[][0]",""); AND TTree::Draw("(ADC[][1]","");
These produce reasonable plots.

However, if I use any higher indices: ADC[][2], ADC[][3], ADC[][4] i get plots with all entries at x=0. Any idea why this might be.?

The most obvious thing is that these indices don’t exist, but if I do a MakeClass and then iterate over these indices I see the correct values.

Thanks.

7

Hi,

Can you try with a newer version of ROOT? (or alternatively can you send me you ROOT file?)?

Cheers,
Philippe.