Hi Rene, I've tracked down the problem. Doing what you suggest works BUT if you then set the title on the axis it somehow resets the scale!!! g->Draw("AP"); g->SetMinimum(0); Works just fine but g->Draw("AP"); g->SetMinimum(0); g2->GetXaxis()->SetTitle("x value"); doesn't work and the scale gets reset. See my macro below demonstrating the problem. Cheers, Jeff. Int_t height=2000; Int_t numPoints=10; TGraph* g=new TGraph(numPoints); TGraph* g2=new TGraph(numPoints); TGraph* g3=new TGraph(numPoints); TGraph* g4=new TGraph(numPoints); for (Int_t i=0;i<numPoints;i++){ height+=100; g->SetPoint(i,i,height); g2->SetPoint(i,i,height); g3->SetPoint(i,i,height); g4->SetPoint(i,i,height); } TCanvas *c=new TCanvas("c","c",0,0,1200,800); c->SetFillColor(0); c->Divide(2,2); //first plot c->cd(1); g->Draw("AP"); g->SetMinimum(0); g->SetTitle("Test plot - I work"); g->SetMarkerStyle(3); g->SetMarkerColor(2); g->SetMarkerSize(0.2); //second plot c->cd(2); g2->Draw("AP"); g2->SetMinimum(0); g2->SetTitle("Test plot - I don't work (x-axis matters)"); g2->SetMarkerStyle(3); g2->SetMarkerColor(2); g2->SetMarkerSize(0.2); g2->GetXaxis()->SetTitle("x value"); //g2->GetXaxis()->CenterTitle(); //third plot c->cd(3); g3->Draw("AP"); g3->SetMinimum(0); g3->SetTitle("Test plot - I don't work (y-axis matters)"); g3->SetMarkerStyle(3); g3->SetMarkerColor(2); g3->SetMarkerSize(0.2); g3->GetXaxis()->SetTitle("x value"); g3->GetXaxis()->CenterTitle(); g3->GetYaxis()->SetTitle("height"); g3->GetYaxis()->CenterTitle(); //fourth plot c->cd(4); g4->Draw("AP"); g4->SetMinimum(0); g4->SetTitle("Test plot - I work (SetMin last)"); g4->SetMarkerStyle(3); g4->SetMarkerColor(2); g4->SetMarkerSize(0.2); g4->GetXaxis()->SetTitle("x value"); g4->GetXaxis()->CenterTitle(); g4->GetYaxis()->SetTitle("height"); g4->GetYaxis()->CenterTitle(); //call again right at the end to sort it out!!!! g4->SetMinimum(0); ******************************************** Jeffrey Hartnell, Oxford/RAL DPhil student. Email: jeffrey.hartnell@physics.ox.ac.uk Phone numbers, addresses etc on website: http://www-pnp.physics.ox.ac.uk/~hartnell/ ******************************************** ----- Original Message ----- From: "Rene Brun" <brun@pcbrun.cern.ch> To: "Jeff Hartnell" <jeffrey.hartnell@physics.ox.ac.uk> Cc: <roottalk@cern.ch> Sent: Friday, December 06, 2002 2:44 PM Subject: Re: [ROOT] TGraph & SetMinimum > Hi Jeff, > > What you do should work > g->Draw("ap"); > g->SetMinimum(0); > > if not, please send me a short but running script showing the problem. > > Rene Brun > > On Fri, 6 Dec 2002, Jeff Hartnell wrote: > > > Hi, > > It seems to be impossible to override the automatic axis scaling in > > TGraph when you draw it with the "a" option. > > > > I found this in the digest: > > > > From: Rene Brun (Rene.Brun@cern.ch) > > Date: Wed Mar 20 2002 - 10:33:17 MET > > > > a.. Next message: Rene Brun: "Re: [ROOT] TGaxis" > > b.. Previous message: Rene Brun: "Re: [ROOT] TGeant3, TGeant4 from > > AliSoft" > > c.. In reply to: Steffen Grohmann: "[ROOT] SetRangeUser Problem on > > Y-axis" > > d.. Messages sorted by: [ date ] [ thread ] [ subject ] [ author ] > > > > ---------------------------------------------------------------------- -- > > -------- > > > > > > Hi Steffen, > > > > When you use the option "a" in TAxis::Draw, the axis limits are > > automatically recomputed from the range of the actual Y values. > > You can force a max/min of the y axis via TAxis::SetMaximum/SetMinimum. > > An alternative solution is to use TPad::DrawFrame. > > > > Rene Brun > > > > but TAxis doesn't have SetMaximum or minimum does it? > > > > I do this: > > > > gAdcPhNear[l]->Draw("AP"); > > gAdcPhNear[l]->SetMinimum(0); > > > > but it still gets drawn with the minimum above zero. Why doesn't this > > work? Can it be made to work? > > > > Has anyone found a solution to this problem? I could always draw a > > histogram first with the appropriate scale, but that's ugly! > > Thanks, > > Jeff. > > > > p.s. using latest root on redhat 7.3.1 > > > > >
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