Re: Problems with TGraph
Rene Brun (Rene.Brun@cern.ch)
Thu, 16 Oct 1997 15:04:16 +0200
ROHLFS Reiner wrote:
>
> Hi,
>
> I want to draw a graph on a pad but define the area the graph uses on the pad
> by myself. I found the function TPad::RangeAxis(). But the graph looks always
> the same independent of the parameter values of this function or if I don't
> call this function at all.
> It is the same situation with the function TPad::Range();
>
> Here is my test macro:
>
> {
>
> gROOT->Reset();
>
> // Create a new canvas.
> c1 = new TCanvas("c1","canvas",50,10,600,300);
>
> // create a pad
> pad = new TPad("p1", "pad", 0.05, 0.05, 0.95, 0.95);
> pad->SetFillColor(3);
> pad->SetBorderSize(0);
> pad->RangeAxis(0.2, 0.2, 0.5, 0.8);
> pad->Range(0.0, 0.0, 40., 40.);
> pad->Draw();
>
> pad->cd();
> // create a graph
> Float_t x[] = {8., 12.5, 14.9, 25.8, 30.2};
> Float_t y[] = {16., 14.3, 20.3, 23.5, 29.9};
> graph = new TGraph(5, x, y);
> graph->Draw("AL");
>
> }
>
> If I want to define the Range by pressing the right mouse button on the pad and
> selecting Range and defining new values (for example X1 = 12.45) nothing
> happens but two new strange lines appear on the pad.
>
> Is it the wrong function I call or do I miss something?
The problem with your macro above is that you call graph->Draw
with the option "A". This option indicates that you want to
automatically
compute the range from the graph values. Root will leave about 10 per
cent
margin on the x and y axis.
If you want to have (if I understand correctly!) axis range not
connected to the graph range, you should
graph->Draw("L")
create two TGAxis objects to paint the axis where you want
and with your specified values.
In version 1.03, I introduced a new function TPad::DrawFrame to force
an empty frame with the x and y axis drawn.
Here is a modified version of your macro taking advantage of this
new function:
{
gROOT->Reset();
// Create a new canvas.
c1 = new TCanvas("c1","canvas",50,10,600,300);
// create a pad
pad = new TPad("p1", "pad", 0.05, 0.05, 0.95, 0.95);
pad->Draw();
pad->cd();
// create a graph
Float_t x[] = {8., 12.5, 14.9, 25.8, 30.2};
Float_t y[] = {16., 14.3, 20.3, 23.5, 29.9};
pad->DrawFrame(0., 10, 40, 35);
graph = new TGraph(5, x, y);
graph->Draw("L");
}
Rene Brun