Re: [ROOT] Can I fit a gaussian on to a ntuple plot... how?

From: Rene Brun (Rene.Brun@cern.ch)
Date: Fri Apr 12 2002 - 22:16:44 MEST


In my previous mail, I forgot to answer one of your questions about
getting the plot of the fit results. Simply add the statement indicated
below

Rene Brun

On Fri, 12 Apr 2002, Rene Brun wrote:

> Hi Shiva,
> 
> OK, run $ROOTSYS/tutorials/cernstaff.C. You get the file cernstaff.root.
> Now in a Root session, do:
> 
>  TFile f("cernstaff.root");
>  T.SetFillColor(38);
   gStyle->SetOptFit();  //<=======================new line
>  T.Fit("gaus","Age>>hAge","Grade>10","","bar2")
> 
> Rene Brun
> 
> 
> On Fri, 12 Apr 2002, Siva Subramania wrote:
> 
> > Dear Rene,
> > I used the same thing before giving the mail also, actually, when I 
> > use ntuple.Fit("gaus","area"); I am getting a table of values of the 
> > mean, sigma, error, step size, first derivative, and so on.  But 
> > nothing is plotted on the graph ie over the ntuple. I also have given 
> > ntuple.SetOptFit(1111), still, nothing is displayed about the 
> > probability, Chi2 and others on the Legend.  So what to do now? I 
> > tried a lot of things, but couldn't figure out. Still trying. Can you 
> > do me a favor, try to give a solution based on the the TNtuple Example 
> > script or the TTree Example given in the documentation. You have 
> > plotted an ntuple graph, plotting the age distribution in the same 
> > chapter on Trees, try to tell me, how would you now fit a gaussian 
> > distribution to the age distribution shown. Please.... reply.
> > Thanx,
> > Yours,
> > Shiva.
> > 
> > On Thu, 11 Apr 2002, Rene Brun wrote:
> > 
> > > Hi Shiva,
> > > 
> > > See TTree::Fit
> > > 
> > > example:
> > >    ntuple.Fit("gaus","px")
> > > 
> > > Rene Brun
> > > 
> > > On Thu, 11 Apr 2002, Siva Subramania wrote:
> > > 
> > > > Hi,
> > > > I am new to using ntuples, I managed to understand about ntuples, and I 
> > > > think, they are nearly the same as histograms, so if I can fit a gaussian 
> > > > on to a histogram, I should be able to - on an ntuple also, but
> > > > I am having trouble with fitting a gaussian function on to a ntuple plot. 
> > > > Can I do it or not? If I can, then how to?  Please reply.
> > > > Thanx,
> > > > Yours,
> > > > Shiva.
> > > > 
> > > 
> > > 
> > 
> 



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