Histogram from leaf of tree

[tanmaya_shree]

I have a root file with a tree. I need to write a macro to access the histogram from the tree.
Opening the root file in the terminal and using the command
tree.Draw(“leafname”)
gives me the histogram.

But I need to write a macro and access the histogram.

Thanks!

[Wile_E_Coyote]

See “Retrieving the result of Draw” in: TTree::Draw

[couet]

tree.Draw("leafname");
auto h1 = (TH1F*)gPad->GetPrimitive("htemp"); 

[tanmaya_shree]

No I am getting some error.

I am trying something like this:

TLeaf *leaf = tree->GetLeaf(“Mult”);
for (Int_t i=0; i<entries; i++){
leaf->GetBranch()->GetEntry(i);
myhist->Fill(leaf->GetValue());
}
myhist->Draw();

[couet]

You have the wrong quotes:
try:

TLeaf *leaf = tree->GetLeaf("Mult");

[tanmaya_shree]

TH1F *myhist = new TH1F();
TLeaf *leaf = tree->GetLeaf(“Mult”);
for (Int_t i=0; i<entries; i++){
leaf->GetBranch()->GetEntry(i);
myhist->Fill(leaf->GetValue());
}
myhist->Draw();

I tried but I am getting empty histogram. I copied that line of code. (quotes line)

[couet]

Can you post something complete we can run ? for instance, in your example we do not know what entries is…

[tanmaya_shree]

The root file that I am using is large. But here is the link.
https://drive.google.com/file/d/1KEwynNDrXrOGenniBhYhZFwGuFHTtAAu/view?usp=sharing
A1.C (4.6 KB)

[couet]

All your data are in Overflow. You did not specify the histogram limits.

[tanmaya_shree]

Any solution for that?

[couet]

   double xmin = ???? ;// should be defined
   double xmax = ???? ; // should be defined
   int nbins = ???; // should be defined
   TH1F *myhist = new TH1F("myhist", "myhist", nbins, xmin, xmax);

[tanmaya_shree]

So can I obtain those values from the command line. Like when I use the command line and open the root file and draw the histogram using tree.Draw(“leafname”) command.

[Wile_E_Coyote]

Try with:
TH1F *myhist = new TH1F("myhist", "myhist", 100, 0., 0.); // automatic binning

[tanmaya_shree]

Okay so I have some doubts. In the first picture when I do .ls, there are two trees. current cycle and backup cycle. I don’t understand why.
And I find two different histograms with different number of entries by viewing it in TBrowser l.
But using the macro and finding the histogram it gives me 10000 entries (c1.png).

[Wile_E_Coyote]

Aux;1 aux;2 aux3;

Hello! I’m filling a tree and after I, sometimes, get this funny behavior AUX;1 AUX;2 with the same histograms inside but with different events in each ;1 and ;2… Can somebody please tell me why this is happening? Many thanks, Stefanos