SetContour in TGraph2D

ROOT
1

Hi
I have a TGraph2D and I want to increase the number of Contours when drawing the TGraph2D with the option colz.
I am also asking myself how I can access the palette via a script in order to move it to the right spot.

Cheers
Felix

2

You can set the number of contours as shown here.

You can move a palette as demonstrated here:

void movepal()
{
   TCanvas *myCanvas = new TCanvas("myCanvas", "myCanvas",5,44,550,550);
   gStyle->SetOptFit(1);
   gStyle->SetOptStat(0);
   myCanvas->Range(-0.8247861,-0.8247861,0.8247861,0.8247861);
   myCanvas->SetFillColor(10);
   myCanvas->SetBorderMode(0);
   myCanvas->SetBorderSize(0);
   myCanvas->SetTickx();
   myCanvas->SetTicky();
   myCanvas->SetLeftMargin(0.15);
   myCanvas->SetRightMargin(0.15);
   myCanvas->SetTopMargin(0.15);
   myCanvas->SetBottomMargin(0.15);
   myCanvas->SetFrameFillColor(0);
   myCanvas->SetFrameBorderMode(0);

   TH1 *h_myHisto = new TH2D("h_myHisto","",61,-0.0000107,0.0000107,61,-0.00085,0.00085);

   int binx(1), biny(1);
   for(int i = -30; i <=30; i++){
     biny=1;
     for(int j = -30; j <=30; j++){
       double x = double(i)/10.;
       double y = double(j)/10.;
       h_myHisto->SetBinContent(binx,biny,(x*x + y*y ));
       biny++;
     }
     binx++;
   }
   //Set up the colours I wish to use:
   const Int_t ncol = 9;
   Int_t colors[ncol];
   TColor *col;
   Double_t dg=1.0/(1.0*(Double_t)ncol);
   Double_t grey=0;
   for (Int_t i=0; i<ncol; i++) {
     colors[i]= i+101;
     if (gROOT->GetColor(colors[i])) {
       gROOT->GetColor(colors[i])->SetRGB(grey, grey, grey);
     } else {
       TColor *c = new TColor(colors[i], grey, grey, grey);
     }
     grey = grey+dg;
   }

   h_myHisto->SetContour(ncol);
   gStyle->SetPalette(ncol,colors);
   gStyle->SetOptStat(0);
   h_myHisto->SetMaximum(9);

   h_myHisto->GetXaxis()->SetTitle("X axis");
   h_myHisto->GetXaxis()->SetNdivisions(-6);
   h_myHisto->GetXaxis()->SetLabelOffset(0.015);
   h_myHisto->GetXaxis()->SetLabelSize(0.035);
   h_myHisto->GetXaxis()->SetTitleSize(0.035);
   h_myHisto->GetXaxis()->SetTitleOffset(1.2);
   h_myHisto->GetYaxis()->SetTitle("Y axis");
   h_myHisto->GetYaxis()->SetNdivisions(-6);
   h_myHisto->GetYaxis()->SetLabelOffset(0.015);
   h_myHisto->GetYaxis()->SetLabelSize(0.035);
   h_myHisto->GetYaxis()->SetTitleSize(0.035);
   h_myHisto->GetYaxis()->SetTitleOffset(2.4);
 //  h_myHisto->GetZaxis()->SetLabelSize(0.035);
 //  h_myHisto->GetZaxis()->SetTitleSize(0.035);
 //  h_myHisto->GetZaxis()->SetTickLength(0.35);
   h_myHisto->Draw("cont4z");

   myCanvas->Update();
   TPaletteAxis *palette = (TPaletteAxis*)h_myHisto->GetListOfFunctions()->FindObject("palette");
   palette->SetX1NDC(0.9);
   palette->SetX2NDC(0.95);
   palette->SetY1NDC(0.2);
   palette->SetY2NDC(0.8);
   myCanvas->Modified();
   myCanvas->Update();
}
3

Hi
I jsut figured it out.
There is a 2D Histogram drawn, which one can access via TGraph2D::GetHistogram()

Perhaps it would be nice to somewhere mention it in the description…

1 Like
4

root.cern.ch/root/htmldoc/TGraph … tHistogram

5

Maybe one can mention it in part at the very beginning…
That’s where I would expect something like that, especially this doesn’t seems to be the most intuitive way to access the plot…
Perhaps after:

[quote]Specific drawing options can be used to paint a TGraph2D:
…
A TGraph2D can be also drawn with ANY options valid to draw a 2D histogram.
When a TGraph2D is drawn with one of the 2D histogram drawing option, a intermediate 2D histogram is filled using the Delaunay triangles technique to interpolate the data set.[/quote]
THis is already helpful but does not tell you HOW one can access it…

6

Done. Thanks.