Hi Mat,
You have two options
-option 1
t1->Draw("APHOE>>h1");
t1->Draw("BPHOE>>+h1"); // add to existing h1
-option 2
t1->Draw("APHOE>>h1");
t1->Draw("BPHOE>>h2");
TH1F *h1 = (TH1F*)gDirectory->Get("h1");
TH1F *h2 = (TH1F*)gDirectory->Get("h2");
h1->Add(h2);
see doc of TTree::Draw, eg at:
http://root.cern.ch/root/htmldoc/src/TTree.cxx.html#TTree:Draw
Rene Brun
On Fri, 9 Aug 2002, matthew dunseth wood wrote:
> I am trying to add two histograms that I generated with TTree::Draw. The
> commands I typed are as follows:
>
> TFile f("atlfast.root");
> TTree *t1 = (TTree*)f.Get("Atlfast/50");
>
> t1->Draw("APHOE>>h1");
> t1->Draw("BPHOE>>h2");
>
> h1->Add(h2);
>
> When I attempt to add the histograms I get the following:
>
> Error: Symbol h2 is not defined in current scope
> FILE:/tmp/filewYtM0M_cint LINE:1
> *** Interpreter error recovered ***
>
> Why is h2 not defined in current scope? For that matter what is the
> current scope? My knowledge of C++ is quite rudimentary so excuse me if
> the answer to this is obvious.
>
> Matthew Wood
>
>
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