Is it possible to invoke interactive minuit from within ROOT? I.e., the
equivalent of 'h/fit 100 myfunc.f m' in paw? The ROOT fit provides most of
the options of paw, but not this one. The 'm' option in ROOT seems to be
something different.
I've looked in TMinuit, TF, and TH1 classes, but have not been able to find
anyway to get to the interactive interface of minuit or some alternative.
Art Snyder at SLAC
----- Original Message -----
From: "Rene Brun" <Rene.Brun@cern.ch>
To: "Valeri Fine" <fine@bnl.gov>
Cc: <roottalk@pcroot.cern.ch>
Sent: Friday, November 30, 2001 11:14 PM
Subject: Re: [ROOT] tiny Bug in root
> Hi Valery,
>
> I am sorry, but the solution proposed by Kurt is correct.
> Concerning the precision problem in tests like x==0, you can
> always replace them in the expression by x<epsilon.
>
> TF1 has already some logic (when drawing) to "discover" an asymptotic
> behaviour in cases where a division by 0 is found. This logic could be
> extended to TFormula::Eval and TF1::Eval. When a division by 0 is found,
> an additional pass could be done automatically to evaluate the derivatives
> around the point x and estimate the point with a linear or parabolic
> interpolation. I was planning to implement this algorithm. However,
> if somebody has a better idea, let me know.
> Obviously this makes sense only for interpreted functions (TFormula).
>
> Rene Brun
>
> On Fri, 30 Nov 2001, Valeri Fine wrote:
>
> >
> >
> >
> > > Hi,
> > >
> > > there is a way to obtain the desired behaviour by defining the
function
> > > in the proper way:
> > >
> > > root [0] TF1* f1 = new TF1("f1","(sin(x)/x)*(x>0.0)+
1.0*(x==0.0)",0,10)
> >
> > I am not sure this trick helps much because the quantity of the
"floating point"
> > numbers is limited rather infinite as the pure math claims for "real"
numbers
> > (see some numerical calculation book or "Fortran language manual" for
further explanation)
> > and the number of points between any two floating-points is finite too.
> > The books explain why one can not rely on the floating-point expression
like "x == 0.0" either.
> > As result the expression above is not better then the oriogibnal one but
more complex to understand
> > At least the same result one can get with
> >
> > Float_t epsilon = 0.0001; // How to choose that epsilon many books
explain.
> > TF1* f1 = new TF1("f1","(sin(x)/x),epsilon,10)
> >
> > Hope this helps,
> >
> > Best regardes, Valeri
> >
> > > root [1] f->Eval(0)
> > > (Double_t)1.00000000000000000e+00
> > > root [3] f->Eval(1.0)
> > > (Double_t)8.41470984807896505e-01
> > >
> > > I'm not sure whether you run into problems when doing a fit with this,
though.
> > >
> > > best,
> > > Kurt
> > >
> > > > > Dear ROOTERs,
> > > > >
> > > > > I have a test on the following code:
> > > > >
> > > > > TF1 f1("func1", "sin(x)/x", 0, 10)
> > > > > f1.Eval(0),
> > > > >
> > > > >
> > > > > It gives the value 0 instead of 1.
> > >
> > > --
> > > Kurt Rinnert, University of Karlsruhe (TH) - Faculty for Physics
> > >
> >
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