Using different y-axis ranges in TMultiGraph

ROOT
1

I’m trying to make a graph with different data sets and 2 different y axis scales. The first data set will use the first scale (which I want displayed on the left), and all the rest of the data sets will use the second scale (which should appear at the right). I am using TMultiGraph and I am very confused. The code I have displays both scales at the left and the right and puts all graphs on the second scale, so that I can’t even see the first data set. Here is the code I have:

TMultiGraph *mg1 = new TMultiGraph();
TGraph *gr0=new TGraph(graphindex[0],grtimes[0],grdata[0]);
gr0->SetLineColor(1000);
gr0->SetMinimum(-3);
gr0->SetMaximum(13);
mg1->Add(gr0,"APL");

TGraph *gr1=new TGraph(graphindex[1],grtimes[1],grdata[1]);
gr1->SetLineColor(1002);
gr1->SetMinimum(-1);
gr1->SetMaximum(2);
mg1->Add(gr1,"ALY+");

TGraph *gr2=new TGraph(graphindex[2],grtimes[2],grdata[2]);
gr2->SetLineColor(1004);
mg1->Add(gr2);

fC1->cd();
fC1->Clear();
fC1->SetTicks(0,2);
mg1->Draw();
fC1->Modified(); 
fC1->Update();

Any pointers would be most appreciated. I have searched all the documentation I could find but I have not been able to find an example of this.

Thanks.

2

You need to create a second pad. Your example is not complete so It is difficult for me to modify it to make it work. Here is one showing what I mean:

{
   TCanvas *c1 = new TCanvas("c1","c1",600,600);
   TPad *pad1 = new TPad("pad1","",0,0,1,1);
   TPad *pad2 = new TPad("pad2","",0,0,1,1);
   pad2->SetFillStyle(4000); //will be transparent
   pad2->SetFrameFillStyle(0);


   TH2F *h1 = new TH2F("h1","h1",40,-4,4,40,-4,4);
   TH2F *h2 = new TH2F("h2","h2",40,-40,40,40,-40,40);
   Double_t a,b;
   for (Int_t i=0;i<5000;i++) {
      gRandom->Rannor(a,b);
      h1->Fill(a-1.5,b-1.5);
      h2->Fill(10*a+1.5,10*b+1.5);
   }

   pad1->Draw();
   pad1->cd();
   h1->Draw("");

   pad2->Draw();
   pad2->cd();
   h2->SetMarkerColor(kRed);
   h2->Draw("X+Y+");
}
1 Like
3

Thanks for the reply. I have seen that example elsewhere and I tried to modify it to meet my needs but it doesn’t seem to work with TGraph. Is there any way I can do it with TMultiGraph or even TGraph? Thanks.

4

Attached is an other example using multigraphs.
multig2.C (3.19 KB)

5

Thanks for the example. I put it in my program and got it working and I didn’t even need to use TMultiGraph.

6

Hi,

I also want to draw some data with TMultiGraph. In the end it also should have two different y-axis.
My first step was the try to draw the y-axis at the right side with Draw(“LPAY+”). But it seems to me as if TMultiGraph ignores the drawing option “Y+” . Here I made a simple example:

{
double x[5] = {1,2,3,4,5};
double y[5] = {3,4,2,3,4};

TCanvas *c1 = new TCanvas("c1", "c1");

TGraph *gr = new TGraph(5,x,y);
TMultiGraph *mg  = new TMultiGraph();

mg->Add(gr, "LPY+");
mg->Draw("LPAY+");
}

I run your program “multig2.C”. If I understood it correctly, it was meant to set the boolean drawMultiGraphs from false to true, for the case I want to have it drawn with MultiGraphs. But if I do this, the result is the same, as before…the right axis is still on the left.
Can you help me?

Thanks
Luisa

7

Yes … Y+ is ignored… on workaround could be to draw a frame first using Y+ and draw the multigraph on top but you will lose the automatic scaling over the graph collection:

{
double x[5] = {1,2,3,4,5};
double y[5] = {3,4,2,3,4};

TCanvas *c1 = new TCanvas("c1", "c1");

TGraph *gr = new TGraph(5,x,y);
gr->Draw("APY+");

TMultiGraph *mg  = new TMultiGraph();

mg->Add(gr, "L");
mg->Draw();
}
8

Thank you very much.
Then I’ll have to make the workaround.

9

Hi

Maybe a heretical question, but why TGMultigraph ignors Y+ and X+?

Cheers,
delos

10

I do not know. I need to check. do you have a small reproducer ?

11

Hi couet

Sorry for answering so late but I was working on a different solution.
Actually, I wanted to create two pads with two multigraphs. One with two line graphs and the axes on the left and bottom respectively. The other graph should have a different y-scale, a line and a scatter graph (like in the picture). Since I needed custom markers (numbers like in the pic) I chose to use TLatex-text I just added to the pad with the respective xy coordinates.
In the beginning I tried something like this (very short version of what I remember what I tried):

	MHC1 = new TGraph(n,date,currentMHC4);
	MHC6 = new TGraph(n,date,currentMHC6);
	MYC1 = new TGraph(n,date,currentMYC1);
	SCATTER = new TGraph(n,date,nPOINTS);
	
	mg  = new TMultiGraph();
	mg2  = new TMultiGraph();       
	pad1 = new TPad("pad1","",0.03,0,0.73,1);
	pad2 = new TPad("pad2","",0,0,1,1);
	pad1->Draw();
	pad1->cd();
	mg->Add(MHC1,"LPY");
	mg->Add(MHC6,"LP");
	mg->Draw("ALP");
	
	pad2->Draw();
	pad2->cd();
	mg2->Add(MYC1,"LPAY+X++");
	mg2->Add(SCATTER,"LPAY+X+");
	mg2->->Draw("LPAY+X+");

I also tried different combinations of “LAPYX+” aso.
The next question would have been wether there is the possibility of custom markers.

multigs.jpg725×707 51.9 KB


Cheers,
delos

12

No