TGraph2D and marker color % z value

ROOT
1

Hello,

similarly to option colz with TH2 bins (or TGraph2D), I would like to draw a TGraph2D on a 2D plane with a different marker color proportionnal to z value for every point. Is it now feasible ?

Thanks,
Renaud.

2

This is the option PCOL
See:
root.cern.ch/root/html/TGraph2D. … aph2D:Draw

3

[quote=“couet”]This is the option PCOL
See:
root.cern.ch/root/html/TGraph2D. … aph2D:Draw[/quote]

I am looking for the same function. As far as I know, the PCOL option draws a graph in a 3D space, but I would like to draw it on a 2D plane. I can manually do it putting number of TMarker and choosing colors from TPaletteAxis. But I would like to do the same thing in an easier way.

4

This option draws a graph in 3D. The z-value is mapped on both the Z position and the color map. Simply change the angles to the appropriate way (to see the graph from top) and you will get what you are looking for.

5

Thank you, Olivier. Yes. SetPhi and SetTheta work fine. But it seems that it doesn’t work when I Draw(“pcol same”) on other pre-drawn 2D histograms.

6 
void graph2dsame4()
{
   gStyle->SetOptStat(0);
   gStyle->SetOptFit(1111);

   TCanvas *c = new TCanvas("c","Graph2D example",0,0,800,800);

   TH3F *frame3d = new TH3F("frame3d","frame3d",10,0,10,10,1,10,10,0,10);
   frame3d->Draw();

   Double_t x1[4] = {1,1,2,2};
   Double_t y1[4] = {1,2,1,2};
   Double_t z1[4] = {1,2,3,4};
   TGraph2D *g2d1 = new TGraph2D(4,x1,y1,z1);
   g2d1->SetMarkerStyle(20);   
   g2d1->Draw("PCOL SAME");  

   Double_t x2[4] = {5,5,7,7};
   Double_t y2[4] = {5,7,5,7};
   Double_t z2[4] = {5,7,3,8};
   TGraph2D *g2d2 = new TGraph2D(4,x2,y2,z2);
   g2d2->SetMarkerStyle(20);

   g2d2->Draw("PCOL SAME");
}