Re: [ROOT] 2D Fit autoscaling problem

From: steven staelens (steven.staelens@rug.ac.be)
Date: Tue Mar 18 2003 - 17:36:03 MET


root Version 3.05/01 on Intel Linux RH 7.1


        Hi Rene,

Rene Brun wrote:

> Hi Steven,
>
> For making a TGraph out of a TTree, see section:
>   "How to obtain more info from TTree::Draw"
> in the documentation of TTree::Draw at:
>    http://root.cern.ch/root/htmldoc/TTree.html
>
> Concerning your question about making a TGraph out of a TF2,
> I do not understand what you mean. There is a mismatch with dimensions.
>

I also concluded this fact, which rules out the possibility of using
multigraphs to avoid the autoscaling problem, right ?  I still haven't solved
the problem yet (...although I'm trying).  Do you perhaps have another
suggestion to solve my particular 2dfit problem (a typical example is in the
2dfit.gif file of a former mail I've posted), in particular to avoid the
autoscaling ?

many thanks for your first reply,

best regards,

Steven

>
> Rene Brun
>
>  steven staelens wrote:
> >
> > root Version 3.05/01 on Intel Linux RH 7.1
> >
> >         Hi ,
> >
> > In addition to a former mail I narrowed my problem down to the
> > following:
> >
> > I have fitted a twodimensional function to a twodimensional histogram as
> > it should following ROOT user guide lines.  The fit seems to be OK, but
> > to be really sure I have to plot it on top of the lego plot of the
> > histogram.  When I do so, the maximum value of my histogram is set equal
> > to the maximum of my 2D fit.  In my case, this is absolutely not
> > wanted.  I've read on the ROOT digest that this is normal and that it
> > can be solved by using a MultiGraph.
> >
> > Being a ROOT newbie however I don't know how to switch the drawings of
> > my TF2 and of my TH2F into a TGraph.  I've tried in the following
> > pathetic way:
> >
> > TGraph *f2D = new TGraph()
> > h2D->Draw(">>t1")
> >
> > but I realize this is not the way it should be.
> >
> > Can somebody perhaps help me out by giving an example on how to change a
> > 2D histogram drawing into a TGraph object and the same question for a
> > twodimensional function.  When this is solved I can then easily do:
> >
> > TMultigraph *mg = new TMultiGraph()
> > mg->Add(gr1)
> > mg->Add(gr2)
> > mg->Draw()
> >
> > and my problem will be solved.
> >
> > Thanks in advance,
> >
> > best regards,
> >
> > Steven
> >
> > S. Staelens
> > Ghent University
> > ELIS / Medisip
> > Proeftuinstraat 86
> > B-9000 Gent
> > tel. 0032 9 264 66 28
> > fax. 0032 9 264 66 18
> > email: Steven.Staelens@rug.ac.be



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