Hi Stefan,
You must write back the modified and new objects to the file.
The file mmust be opened in update mode.
To write back the modified/new objects, two possibilities
1- write each of them individually to the file, eg
pt_sig_teamlt18.Write();
2 -write all objects to the file with file->Write();
In your case, option 2 is probably the best.
Rene Brun
Stefan Stonjek wrote:
>
> Hello Root Users,
>
> I have a problem with writing a histogram to a specific file.
>
> It is no problem to read the allready existig histos in this program. They
> are already filled in the same program and the "print" command clearly
> indicated that the new histogram contains usefull date. But these data
> does not end up in the file.
>
> Here is the code in question. It is just an excerpt from a much longer
> program with many subroutines.
>
> TH1F *pt_gcc_sig_etamlt18 = (TH1F*)hfile->Get("pt_gcc_sig_etamlt18");
> TH1F *pt_wcc_sig_etamlt18 = (TH1F*)hfile->Get("pt_wcc_sig_etamlt18");
> hfile->cd();
> TH1F pt_sig_etamlt18 = ( *pt_gcc_sig_etamlt18 - *pt_wcc_sig_etamlt18);
> pt_sig_etamlt18.SetName("pt_sig_etamlt18");
> pt_sig_etamlt18.SetDirectory(hfile);
> pt_sig_etamlt18.Print("all");
>
> Mayby it is just a stupid mistake but I hope someone is able to help me.
>
> Tschuess
> Stefan
>
> ********* Stefan Stonjek *********
> ***** DESY / ZEUS *****
> ***** Stefan.Stonjek@desy.de *****
> ********* Tel.: +49-40-8998-3159 *********
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