Dimension of graphical object

Dear all,

i’m facing a very basic issue.

I have TH2F plot where i need to put a measurement and display the correlation among the two variables
with an ellipse. How can i set the two radius of the ellipse so that they have the right dimension compared to x-y axes? I guess i need some conversion to pad coordinate system…thanks in advance for any help!


see example below


void circle() { //a canvas with a fix aspect ratio TCanvas *c1 = new TCanvas("c1"); Double_t w = gPad->GetWw()*gPad->GetAbsWNDC(); Double_t h = gPad->GetWh()*gPad->GetAbsHNDC(); Double_t xmin = 0; Double_t xmax = 100; Double_t ymin = 0; Double_t ymax = xmax*h/w; c1->SetFixedAspectRatio(); c1->Range(xmin,ymin,xmax,ymax); TArc *arc = new TArc(50,50,10); arc->Draw(); }