Getting Values from TTree events

Newbie
1

Hi,

Im trying to get values from a tree wich have several entries , or instances per event. I’m trying to do this as

Double_t energy;
mytree->SetBranchAddress(“myenergy”,&energy)

then, if i do

mytree->GetEntry(# place a number)
(int ) 1640

variable energy is always 0, but i know that my tree is not empty.

Thanks in advance.

2

If you don’t know how to deal with your tree, see how various flavours of automatically generated “analysis skeletons” deal with it.

3

What is it that you are trying to accomplish?

file=TFile("myfile.root", "read");
tree=file.Get("tree")

if you’re trying to inspect your tree i prefer to use scan.

tree.Scan("myenergy","","colsize=20")

this will print all the myenergy elements. then you do something similar if you’re trying to draw it with the Draw() function. The syntax will be using -> pointers instead of . operators, since I’m using python (and your using C++).

4

Thanks for your answers,

What im trying to do is to read certain values from a tree , from certain events. I know that i can read values and print them in screen with Scan , but my idea is to save these values into an array, for example.

5

What is the ‘type’ of the branch myenergy (see for example the result of TTree::Print).