Rene Brun
Markus Weiss wrote:
>
> Thank you for your overwhelming support.
>
> but I seem not to have supplied enough information to
> make my problem clear.
>
> My main problem is to find the appropriate class to store
> nonequidistant triples of data, such as:
>
> x y z
> 5.0 178.75 177.847
> 20.0 178.75 177.496
> 2.25 400.7 390.669
> 10.0 400.7 396.195
>
> The function I want to fit to these (and more) datapoints
> is
> z=f(x,y)
>
> by adjusting 3 additional parameters (dalpha, dbeta, dn)
> which modify f().
>
> I was able to produce a TF2 with this "usersupplied" function.
>
> So far so good, but I did not find a way to store these data and
> do a simple: whatever->Fit().
> I tried TGraph, but this one accepts only two column of data, in other
> words z=f(x).
> I tested TNtuple which seems to be the right joice, but the inherited
> method Fit() (from TTree) accepts only a TF1 function, according to
> the reference guide.
>
> Sofar I succeeded by adapting the IFit.C example in the tutorial which
> uses migrad directly.
>
> So, I am still search for the right data-model to take ntuples of
> nonequidistant data and fit a multidimensional function to it, which
> is as easy as the one-dimensional case (Tgraph() and Fit()).
>
> Thanks again,
>
> Markus.
>
> The suggestions to solve my problem follow:
>
> On Sat, 01 May 1999, Faouzi Attallah wrote:
> >I hope Rene agrees with the following syntaxe. In the 2dim-hist case and
> >a usersupplied function as, e.g. a 2dim Polynome of 1st degre one can
> >write:
> >
> > TH2F *Hr ; // the 2-dim host
> > ...
> > pol = new TF2 ("pol","[0]*x + [1]*y + [2]", xmin, xmax, ymin, ymax) ;
> > pol->SetParNames("Ax","Ay","B") ;
> > hr->Fit("pol","R0") ;
> >
>
> I am not sure if the 2dim-hist class is the rigth choice for my data.
>
> On Sat, 01 May 1999, Rene Brun wrote:
> > Please, read the tutorials graph.C and myfit.C
> > You create a TGraph(n,x,y) object with your array of points,
> > then invoke TGraph::Fit with your user defined function.
>
> To my knowledge, TGraph cannot cope with data consisting of
> more than 2 columns (i.e. x,y,z).
>
> --
> ---------------------------------------------------------------------
> Markus Weiss "Ah elbereth glithoniel
> BESSY-2 Projektteam silvren penna miriel"
> e-mail: weiss@abbe.exp.bessy.de phone: +49-30-6392-2941
> ---------------------------------------------------------------------