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root:ttreedraw [2013/06/14 11:09] – nchiap | root:ttreedraw [2013/06/14 11:41] (current) – nchiap | ||
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Alternatively the name of the histogram to be created can be given or the data can be added to an existing histogram. | Alternatively the name of the histogram to be created can be given or the data can be added to an existing histogram. | ||
<code c++> | <code c++> | ||
- | tree-> | + | tree-> |
- | TH1F *hist = gPad-> | + | TH1F *hist = gPad-> |
- | tree-> | + | tree-> |
</ | </ | ||
Line 67: | Line 67: | ||
} | } | ||
</ | </ | ||
+ | |||
+ | ===== Pitfalls ===== | ||
+ | |||
+ | ==== Unable to add to existing histograms ==== | ||
+ | Adding data to an existing histogram will fail, if any file was opened after creating the histogram! | ||
+ | TTree:: | ||
+ | |||
+ | To avoid this make sure to load the input files before you create any histograms or | ||
+ | create a storage file and switch back there after opening any files: | ||
+ | <code c++> | ||
+ | TFile tmp(" | ||
+ | float bins[] = {0, 10, 20, 40, 80}; | ||
+ | TH1F myhist(" | ||
+ | |||
+ | TFile file(" | ||
+ | TTree *tree = file.Get(" | ||
+ | |||
+ | tmp.cd() | ||
+ | tree-> | ||
+ | </ | ||