Rene Brun
Tadeusz Pytlos wrote:
>
> Dear Rooters,
> The TBrowser is a very nice device, but I need to draw a histogram
> from directory in the formal way. I failed trying it in this way
>
> ....
> TFile *hfile=new TFile("prob.root");
> top->cd();
> plane6->cd();
> page = new TCanvas("page","Probability",0,0,500,700);
> page->SetFillColor(10);
> page->Divide(1,1);
>
> Int_t kpad,ans;
> char padname[20];
>
> kpad=0;
> // sprintf(padname,"page_%d",kpad+1);
> // TPad *pad = (TPad*)page->GetPrimitive(padname);
> // pad->cd();
Note that you do not need all these statements. You can directly do
page->cd(1); // now gPad points to the current pad
> pad->SetGrid();
> pad->SetLogy();
> pad->GetFrame()->SetFillColor(42);
> pad->GetFrame()->SetBorderMode(-1);
> pad->GetFrame()->SetBorderSize(5);
> pad->Draw();
>
> char hname[20];
> TH1 *h;
>
> sprintf(hname,"h%d",kpad+12);
> h=(TH1F*)hfile.Get(hname);
You should check here against h=NULL. Very likely hname as encoded
in your sprintf does not exist in the file. CINT correctly generates
the diagnostic below.
> h.SetLineWidth(2);
> h.SetLineStyle(1);
> h.SetLineColor(1);
> h.SetXTitle("k");
> h.SetYTitle("N");
> h.SetMinimum(1e-1);
> h.Draw();
> ....
> }
> The error was just
>
> Processing prob1.C...
> Error: illegal pointer to class object h 0x0 321
> FILE:/home/pytlos/usr/kret/stat33/./prob1.C LINE:90
> NULL
> *** Interpreter error recovered ***
>
> How modify my macro?
> *********************
>
> Next thing. What wrong with f.pwd()? Example below.
A statement like f.pwd() prints the name of the directory f,
not the name of of subdirectory in f where you may be.
If you want to print the name of your current directory, do
gDirectory->pwd();
>
> root [0] TFile *f=new TFile("prob.root")
> root [1] f.ls()
> TFile** prob.root
> TFile* prob.root
> KEY: TDirectory top;1 top
> root [2] f.pwd()
> prob.root:/
> root [3] .pwd
> Current directory: prob.root:/
> Current style: Default
> root [4] top.cd()
> root [5] f.ls()
> TFile** prob.root
> TFile* prob.root
> TDirectory* top top
> KEY: TDirectory plane6;1 plane6
> KEY: TDirectory top;1 top
> root [6] f.pwd()
> prob.root:/
> root [7] .pwd
> Current directory: prob.root:/top
> Current style: Default
> root [8] plane6.cd()
> root [9] f.ls()
> TFile** prob.root
> TFile* prob.root
> TDirectory* top top
> TDirectory* plane6 plane6
> ......
> KEY: TH1S h12;1 h12
> KEY: TDirectory plane6;1 plane6
> KEY: TDirectory top;1 top
> root [10] f.pwd()
> prob.root:/
> root [11] .pwd
> Current directory: prob.root:/top/plane6
> Current style: Default
> root [12]
>
> Thank in advance,
> Tadeusz
>
> --
> Tadeusz Pytlos
> mailto:pytlos@fizwe5.fic.uni.lodz.pl
> Lodz, Poland