I would also recomment you use
gDirectory->Get
instead of
gROOT->FindObject
It will be more efficient.
Rene Brun
lijowski@cosray2.wustl.edu wrote:
>
> Hello,
>
> I have a multiple histograms spread over three subdirectories
> in the root file. I have a following test program to read
> each histogram from one subdirectory inside the loops but with
> no luck except at the beginning when I read a single histogram.
>
> I appreciate any help.
>
> Michal Lijowski
>
> // Tests reading array of histograms from the *.root file
>
> {
> gROOT -> Reset();
>
> TFile *cfile =
> (TFile*)gROOT->GetListOfFiles()->FindObject("charge_hists.root.6");
> if (!cfile) {
> cfile = new TFile("charge_hists.root.6", "READ");
> }
>
> // cfile -> ls();
>
> cfile -> cd("charge_hists.root.6:/TOP/ZEST_LAST_HISTS");
> cfile -> pwd();
>
> TH1F *h1 = (TH1F *) gROOT -> FindObject("ZEST_LAST");
> h1 -> Draw();
>
> Int_t N_TEL = 4;
> char ctel[2], hname[30];
>
> Int_t N_STACK_DET = 9;
> Int_t Range_min = 2;
> Int_t nhists = (N_STACK_DET - Range_min + 1) * N_TEL + 1;
> printf(" nhists = %d\n", nhists);
>
> TH1F *ZEST_LAST_hists[nhists];
>
> Int_t hidx = 0;
>
> for (Int_t itel = 0; itel < N_TEL; itel++) {
> ctel[0] = '\0';
> if (itel == 0) strcat(ctel, "A");
> if (itel == 1) strcat(ctel, "B");
> if (itel == 2) strcat(ctel, "C");
> if (itel == 3) strcat(ctel, "D");
> for (Int_t rr = Range_min; rr < N_STACK_DET; rr++) {
> hname[0] = '\0';
> sprintf(hname, "ZEST_LAST_%s_Range_%1d", ctel, rr);
> TH1F *ZEST_LAST_HISTS[hidx] = (TH1F *) gROOT -> FindOBject(hname);
> // ZEST_LAST_HISTS[hidx] -> (TH1F *) cfile -> Get(hname);
> ZEST_LAST_HISTS[hidx] -> Draw();
> hidx++;
> }
> }
> }
>
> This is a log file.
>
> *******************************************
> * *
> * W E L C O M E to R O O T *
> * *
> * Version 2.00/11 28 August 1998 *
> * *
> * You are welcome to visit our Web site *
> * http://root.cern.ch *
> * *
> *******************************************
>
> CINT/ROOT C/C++ Interpreter version 5.13.69, Aug 22 1998
> Type ? for help. Commands must be C++ statements.
> Enclose multiple statements between { }.
> charge_hists.root.6:/
> Warning in <MakeDefCanvas>: creating a default canvas with name c1
> Error: Can't call TROOT::FindOBject() in current scope FILE:/export/home/lijowski/ace/cris/flight/root/./test_TDirectory.C LINE:42
> nhists = 33
> ZEST_LAST_A_Range_2
> *** Interpreter error recovered ***