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).
--
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Markus Weiss "Ah elbereth glithoniel
BESSY-2 Projektteam silvren penna miriel"
e-mail: weiss@abbe.exp.bessy.de phone: +49-30-6392-2941
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