TTree plot with error bars

ROOT
1

Hello,
If i have

Double_t x[n],
Double_t y[n] and
Double_t dy[n],

where dy[i] is the error of y[i], loaded into a TTree (“x:y:dy”), is it possible to get a plot of y vs. x with error bars.
The closest I came was doing

tree->Draw(“y : x>>hp”,"",“profs”), which sort of works

(although there seem to be some binning issues, since the x values look slightly shifted from the original position), but I’m not sure how to get the error bars on there. Thanks in advance.

2

It is not totally clear what you want to do. Just in case you simply want to draw a graph of N points x[i],y[i] with error bar in y = dy[i] and your data in a Tree,
you can do:

tree.Draw("x:y:dy","","goff"); TGraphErrors g(tree.GetEntries(),tree.GetV1(),tree.GetV2(),0,tree.GetV3()); g.Draw("ap");
Rene

3

Hi,
Thanks for the reply. What I meant was pretty much if it’s possible to do the same straight from the TTree::Draw() [or Fit] function, without having to use TGraphErrors. But this works for me.