Re: Large array size problem in TGraph

  Thank you very much!

 It works well when "lP" option is used.

On Wed, 19 Apr 2006, Rene Brun wrote:

> Do not use the Draw option "CP" when you have so many points
> and use a more optimized algorithm as shown below
>
> Rene Brun
>
>
> {
> gROOT->Reset();
> TCanvas *c1 = new TCanvas("c1"," ",200,10,700,500);
> TH1F *hr = c1->DrawFrame(0.0001,0.00001,1,100);
> c1->SetLogx();
> c1->SetLogy();
> ifstream my("test.dat");
> const Int_t n = 999999;
> TGraph *gr = new TGraph(n);
> Double_t x, y;
> for (Int_t i=0;i<n;i++) {
> my >> x >> y;
> gr->SetPoint(i,x,y);
> }
> printf("finished reading data\n");
> gr->SetLineWidth(2);
> gr->GetXaxis()->SetTitle("x");
> gr->GetYaxis()->SetTitle("f(x)");
> //gr->Draw("CP");
> gr->Draw("lP");
> }
>
>
> On Wed, 19 Apr
> 2006, Ding Hengtong wrote:
>
> >
> > Hi Rooters,
> >
> > I want to plot a data file which has 999999 lines, I used
> > TGraph class in ROOT but I can't get a figure but just a canvas with
> > axis instead.
> >
> > My code is listed below and according to ROOT Guide, Int_t is 4 Bytes,
> > ranges from -2^{31} to 2^{31}-1 and 999999 is actually in this range.
> > And I also tried "Long64_t", by which I still can't get the figure I
> > wanted. I don't know what's wrong.
> >
> > {
> > gROOT->Reset();
> > TCanvas *c1 = new TCanvas("c1"," ",200,10,700,500);
> > TH1F *hr = c1->DrawFrame(0.0001,0.00001,1,100);
> > c1->SetLogx();
> > c1->SetLogy();
> > ifstream my("test.dat");
> > const Int_t n = 999999;
> > Double_t x[n], y[n];
> > for (Int_t i=0;i<n;i++) {
> > my >> x[i] >> y[i];
> > }
> > TGraph *gr = new TGraph(n,x,y);
> > gr->SetLineWidth(2);
> > gr->GetXaxis()->SetTitle("x");
> > gr->GetYaxis()->SetTitle("f(x)");
> > gr->Draw("CP");
> > }
> >
> > Thanks for any help.
> >
> > Regards,
> >
> > Hengtong
> >
> >
>

-- 
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 *             Hengtong Ding                    *                    
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