Matthew R. Nelson wrote:
>
> Dear Rooters,
>
> I would like to add a TPad to a TGraph, with the location of the TPad
> being specified by the XY coordinates of the TGraph. The methods for
> placing a TPad are relative to the coordinates of the next pad up in the
> hierarchy, which in my case is the TCanvas.
>
> Is there a way to either
> a) place a TPad on a TGraph using the TGraph XY coordinates, or
> b) obtain a translation of a pair of XY coordinates to the mother
> TPad/TCanvas coordinates?
>
> I suppose as a last resort, all of the TGraph margins and the X and Y
> ranges could be considered to create such a translation by hand, but I
> would like to avoid that if possible.
>
Hi Matt,
In the attachment, you will find the Root tutorial example graph.C
modified to add a pad connected to one of the graph points.
Rene Brun
{
//
// To see the output of this macro, click begin_html <a href="gif/graph.gif">here</a>. end_html
//
gROOT->Reset();
c1 = new TCanvas("c1","A Simple Graph Example",200,10,700,500);
c1->SetFillColor(42);
c1->SetGridx();
c1->SetGridy();
c1->GetFrame()->SetFillColor(21);
c1->GetFrame()->SetBorderSize(12);
Int_t n = 20;
Float_t x[n], y[n];
for (Int_t i=0;i<n;i++) {
x[i] = i*0.1;
y[i] = 10*sin(x[i]+0.2);
printf(" i %i %f %f \n",i,x[i],y[i]);
}
gr = new TGraph(n,x,y);
gr->SetFillColor(19);
gr->SetLineColor(2);
gr->SetLineWidth(4);
gr->SetMarkerColor(4);
gr->SetMarkerStyle(21);
gr->SetTitle("a simple graph");
gr->Draw("ACP");
//Add axis titles.
//A graph is drawn using the services of the TH1F histogram class.
//The histogram is created by TGraph::Paint.
//TGraph::Paint is called by TCanvas::Update. This function is called by default
//when typing <CR> at the keyboard. In a macro, one must force TCanvas::Update.
c1->Update();
gr->GetHistogram()->SetXTitle("X title");
gr->GetHistogram()->SetYTitle("Y title");
//Add 1 pad connected to graph point 4
Float_t xpad = c1->GetX2() - c1->GetX1();
Float_t ypad = c1->GetY2() - c1->GetY1();
Float_t x1min = (x[4] - c1->GetX1())/xpad; //convert x[4] to NDC
Float_t y1max = (y[4] - c1->GetY1())/ypad; //convert y[4] to NDC
Float_t x1max = x1min + 0.2;
Float_t y1min = y1max - 0.15;
TPad *pad1 = new TPad("p4","pad at point 4",x1min,y1min,x1max,y1max);
pad1->Draw();
}
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