one histogram with changing values in different pads of a canvas

From: Judith Katzy (katzy@nanalpc.phy.uic.edu)
Date: Mon Sep 20 1999 - 21:17:33 MEST 

Hello rooters,

during an analysis loop, I want to fill one histogram, draw it, reset 
it and fill it with a different value, draw it again. It works fine, 
if I do it on the command line, but if I try to do it in a macro, it 
draws the histogram with the last value in all of the pads. See macro
below. 
This behaviour occurs, because TH1::Draw() only attaches a reference to
the pad. According to the documentation, the effective drawing is
performed when the canvas receives a signal to be painted, which is after
a carriage return, in this case at the end of the macro. 
Is there a way to invoke the drawing of the pad before that?

Another  effect is, that if the histogram is drawn with different values 
in different pads and one invokes TCanvas::Print() all histograms are 
replaced  with the histogram containing the latest value. 

Is there a way to work with just one histogram?

cheers,
Judith

{

TCanvas *cw;
if(!cw) cw = new TCanvas("test","test",700,700);
cw->Clear();
cw->Divide(1,2);
TH1D ht("ht","ht",4,0.,3.);

cw->cd(1);
ht.Fill(0.);
ht.Draw();

cw->cd(2);
ht.Reset();
ht.Fill(2.);
ht.Draw();
}

This archive was generated by hypermail 2b29 : Tue Jan 04 2000 - 00:43:39 MET