Hi Harufumi,
Your set of data is an interesting case. In case the y value at the minimum
is smaller than its error bar and a log scale is requested along y,
y -ey is less than 0. In this case, ROOT will automatically compute a new
minimum using ymax/1000.
I will fix the algorithm.
Meanwhile, you can easily circumvent the problem by setting yourself
a minimum for your plot as shown in the following script using your data points
Rene Brun
{
const Int_t n = 7;
Double_t x[n] = {1,2.5,4,7,10,30,60};
Double_t y[n] = {1.5e-11, 3.0e-12, 1.7e-12, 4.0e-13, 4.0e-15,4.0e-14,
2.0e-16};
Double_t yerror[n] =
{4.0e-12,1.0e-12,8.0e-13,1.0e-13,7.0e-15,3.0e-14,4.0e-16};
TCanvas *c1 = new TCanvas("c1");
c1->SetLogx(); c1->SetLogy();
c1->SetGrid();
TGraphErrors *gr = new TGraphErrors(n, x, y, 0, yerror);
gr->SetMarkerStyle(20);
gr->SetMinimum(1e-16);
gr->Draw("AP");
}
Harufumi Tsuchiya wrote:
>
> Hi ROOTers.
>
> I have the data which must be displayed in log scale.
> The data is like below.
>
> x y yerror
> 1.0 1.5e-11 4.0e-12
> 2.5 3.0e-12 1.0e-12
> 4.0 1.7e-12 8.0e-13
> 7.0 4.0e-13 1.0e-13
> 10.0 4.0e-15 7.0e-15
> 30.0 4.0e-14 3.0e-14
> 60.0 2.0e-16 4.0e-16
>
> As I would like to show data with error bars, I used TGraphErrors.
>
> c1->SetLogx(); c1->SetLogy();
> TGraphErrors *gr = new TGraphErrors(ndata, x, y, 0, yerror)
> gr->Draw("AP")
>
> But I could not get all data points with errors.
> As I attached this e-mail, the data point with x = 10.0 and 60.0 were not
> appeared on graph. Other data points appeared together with errorbars.
>
> I thought that if the values of the data points were smaller than errors,
> the data point and the accompanied errors were not drawn.
> Is is correct ?
>
> If someone know the method to avoid the my uncomplete result,
> Please tell me.
> I would like to show all data points with error bars.
>
> I use ROOT v 3.02.06 on IRIX64 and g++ 2.95.2.
>
> Thanks
>
> Harufumi Tsuchiya
>
> --------------------------------------------------------------------------------
>
> Name: c1.gif
> c1.gif Type: GIF Image (Image/Gif)
> Encoding: base64
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