How draw histo from directory

Tadeusz Pytlos (pytlos@fizwe5.fic.uni.lodz.pl)
Tue, 26 May 1998 17:30:27 +0200 (CEST)

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();
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);
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.

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