Stephane, Stephane Plaszczynski wrote: > > OK both work well (even if I don't understnd why the Update() should be > moved...) > see the description of the Canvas Draw/Paint/Update in the Users Guide at pages 106,107 and 111 Rene Brun > thanks for your patience, > > Stephane > > --On Thursday, September 18, 2003 03:07:11 PM +0200 Rene Brun > <Rene.Brun@cern.ch> wrote: > > > > >> --On Thursday, September 18, 2003 12:02:44 PM +0200 Rene Brun > >> <Rene.Brun@cern.ch> wrote: > >> > >> > I don't know what you mean by sigma_y? > >> > If you just want to draw a set of points with eerrors, use TGraphErrors > >> > TGraphErrors(n,x,y,ex,ey) > >> > >> OK. So I guess my question is whether there is an "automated" way of > >> creating this Graph directly from the ntuple entries (I am used to a tool > >> that can do it): something like Draw("y:x") but where each point > >> displayed would have an error bar given by two other ntuple entries > >> "sigmax,sigmay"? > >> > > > > You can do the following > > nt->Draw("x:y:sigmax","sigmay","goff"); > > TGraphErrors g(nt->GetSelectedRows(),nt->GetV1(),nt->GetV2(),nt->V3(), > > nt->GetW()); > > g.Draw("ap"); > > > > see TTree::Draw doc section "How to obtain more info from TTree::Draw" > > > >> > > >> II tried the following unamed script (following your suggestion). It is > >> in "myscript.C" > >> I log in interactively to root and type > >> .x myscript.C > >> but the ntuple points do not appear.... > >> > > > > You should move the c1->Update() statement immediatly after having drawn > > the histogram. See change below
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