Hi Jeff,
Thanks for reporting this interesting sequence. I have fixed this problem
in the CVS version. Meanwhile, you can solve this problem by updating the
canvas after having drawn the 3rd plot
//third plot
c->cd(3);
g3->Draw("AP");
c->Update(); //add this line
The problem is that TGraph::GetAxis creates automatically the histogram
object for plotting and ignores the existing min/max settings.
Rene Brun
Jeff Hartnell wrote:
>
> Hi Rene,
> A couple of months ago I discovered that a TGraph's SetMinimum/Maximum got
> overwritten when you set the title of the axis after plotting it. Thank you
> for fixing this.
>
> I have discovered another similar feature (which has been bugging me (excuse
> pun) for a long time and took hours to track down!).
>
> If you do the following:
> 1.) Create the graph
> 2.) Set it's min/max
> 3.) Fill it with points
> 4.) Plot it
> 5.) Set the axis title
> Then the min/max you set gets overwritten.
>
> If you do the following (swap 2 and 3 around):
> 1.) Create the graph
> 2.) Fill it with points
> 3.) Set it's min/max
> 4.) Plot it
> 5.) Set the axis title
> Then you are ok, so this indicates that it is something to do with the order
> in which you fill with points and set min/max.
>
> However, if you do my first example but don't include step 5 then you are
> also ok, as in:
> 1.) Create the graph
> 2.) Set it's min/max
> 3.) Fill it with points
> 4.) Plot it
> Setting min/max first is ok as long as you don't want to set the title on
> the axis!!!!!!
>
> I have included a little code snippet below illustrating the problem.
> Many thanks,
> Jeff.
>
> P.S. Using latest root.
>
> Int_t height=2000;
> Int_t numPoints=10;
>
> TGraph* g=new TGraph(numPoints);
> TGraph* g2=new TGraph(numPoints);
> TGraph* g3=new TGraph(numPoints);
>
> //set g2 and g3 min/max before SetPoint
> g2->SetMinimum(0);
> g2->SetMaximum(5000);
> g3->SetMinimum(0);
> g3->SetMaximum(5000);
>
> 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);
> }
>
> //set g min/max after SetPoint
> g->SetMinimum(0);
> g->SetMaximum(5000);
>
> TCanvas *c=new TCanvas("c","c",0,0,1200,800);
> c->SetFillColor(0);
> c->Divide(3,1);
>
> //first plot
> c->cd(1);
> g->Draw("AP");
> g->SetTitle("Plot Ok - Min/max set after SetPoint()");
> g->SetMarkerStyle(3);
> g->SetMarkerColor(2);
> g->SetMarkerSize(0.4);
>
> g->GetXaxis()->SetTitle("x Value");
> g->GetYaxis()->SetTitle("Height");
> g->GetXaxis()->CenterTitle();
> g->GetYaxis()->CenterTitle();
>
> //second plot
> c->cd(2);
> g2->Draw("AP");
> g2->SetTitle("Plot Ok - Min/max set before SetPoint() (no axis
> modification)");
> g2->SetMarkerStyle(3);
> g2->SetMarkerColor(2);
> g2->SetMarkerSize(0.4);
>
> //third plot
> c->cd(3);
> g3->Draw("AP");
> g3->SetTitle("Plot NOT Ok - Min/max set before SetPoint() and axis
> modification");
> g3->SetMarkerStyle(3);
> g3->SetMarkerColor(2);
> g3->SetMarkerSize(0.4);
>
> g3->GetXaxis()->SetTitle("x Value");
> g3->GetYaxis()->SetTitle("Height");
> g3->GetXaxis()->CenterTitle();
> g3->GetYaxis()->CenterTitle();
>
> ----- 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 10:09 PM
> Subject: Re: [ROOT] TGraph & SetMinimum
>
> > Hi Jeff,
> >
> > Add the statement
> > c->Update();
> > after your Draw calls, eg:
> >
> > //second plot
> > c->cd(2);
> > g2->Draw("AP");
> > c->Update();
> > g2->SetMinimum(0);
> >
> >
> > //third plot
> > c->cd(3);
> > g3->Draw("AP");
> > c->Update();
> > g3->SetMinimum(0);
> >
> > This is not necessary anymore if you use the development version in CVS.
> >
> > Rene Brun
> >
> > On Fri, 6 Dec 2002, Jeff Hartnell wrote:
> >
> > > 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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