Hello
I have a problem using TGraphErrors:
Somehow the program doesn’ take errors in x-direction into account.
Here’s a simple example:
void error()
{
Double_t x[2]={1,2};
Double_t y[2]={2,4};
Double_t ex[2]={0.3,0.3};
Double_t ey[2]={0.1,0.1};
TCanvas *myc = new TCanvas(“myc”, “Fitting TGraphErrors”);
TGraphErrors *gre3 = new TGraphErrors(2, x, y, 0,ey);
TF1 ploynom=new TF1(“polynom”,“pol1”);
gre3->Draw("a");
gre3->Fit(polynom);
}
Everything is done correctly. But if I replace the 0 in TGraphErrors with ey, the error estimates stay the same even if I take very large errors like in this example. Why doesn’t root take the errors in x-direction into account for the error estimate?
Thanks for your help…