This works in 3.02-03. There is one remaining small problem. When one fits
without the "b" option minuit still claims the "fixed" parameters are
fixed, but they are not. This is likely to confuse people.
With "b" option on it works great.
Thanks again,
Art
A.E. Snyder, Group EC \!c*p?/
SLAC Mail Stop #95 ((. .))
Box 4349 |
Stanford, Ca, USA, 94309 '\|/`
e-mail:snyder@slac.stanford.edu o
phone:650-926-2701 _
http://www.slac.stanford.edu/~snyder BaBar
FAX:650-926-2657 Collaboration
On Mon, 3 Dec 2001, Rene Brun wrote:
> Art,
>
> Here is a small example:
>
> void fixp() {
> TH1F *h = new TH1F("h","test",100,-4,4);
> h->FillRandom("gaus",5000);
> TF1 *e = new TF1("e","pol4",-1,1);
> e->FixParameter(0,160);
> h->Fit("e","br");
> }
>
> Using the option "b" (Boundary) is important. The documentation of TH1::Fit
> says:
>
> //*-* Setting initial conditions
> //*-* ==========================
> //*-* Parameters must be initialized before invoking the Fit function.
> //*-* The setting of the parameter initial values is automatic for the
> //*-* predefined functions : poln, expo, gaus. One can however disable
> //*-* this automatic computation by specifying the option "B".
> //*-* You can specify boundary limits for some or all parameters via
> //*-* f1->SetParLimits(p_number, parmin, parmax);
> //*-* if parmin>=parmax, the parameter is fixed
> //*-* Note that you are not forced to fix the limits for all parameters.
> //*-* For example, if you fit a function with 6 parameters, you can do:
> //*-* func->SetParameters(0,3.1,1.e-6,-1.5,0,100);
> //*-* func->SetParLimits(3,-10,-4);
> //*-* func->FixParameter(4,0);
> //*-* func->SetParLimits(5, 1,1);
> //*-* With this setup, parameters 0->2 can vary freely
> //*-* Parameter 3 has boundaries [-10,-4] with initial value -8
> //*-* Parameter 4 is fixed to 0
> //*-* Parameter 5 is fixed to 100.
> //*-* When the lower limit and upper limit are equal, the parameter is fixed.
> //*-* However to fix a parameter to 0, one must call the FixParameter
> function.
>
> Rene Brun
>
>
> Arthur E. Snyder wrote:
> >
> > The SetParLimits function really seems to be totally ineffective:
> >
> > root [180] efit->GetParameter(0)
> > (Double_t)5.89071269118343935e+02
> > root [181] efit->SetParameter(0,2.0)
> > root [182] efit->GetParameter(0)
> > (Double_t)2.00000000000000000e+00
> > root [183] efit->SetParLimits(0,1.0,1.0)
> >
> > -so parmeter 0 of this function (a "pol4") should be fixed to 2.0
> >
> > root [184] bhist->Fit("e") [note a]
> > FCN=66.7558 FROM MIGRAD STATUS=CONVERGED 134 CALLS 135
> > TOTAL
> > EDM=5.71703e-14 STRATEGY= 1 ERR MATRIX NOT
> > POS-DEF
> > EXT PARAMETER APPROXIMATE STEP FIRST
> > NO. NAME VALUE ERROR SIZE DERIVATIVE
> > 1 p0 5.89071e+02 fixed
> > 2 p1 -3.16776e+03 2.00304e+00 1.51050e-03 8.00435e-08
> > 3 p2 6.43575e+03 3.89200e+00 3.06881e-03 -8.40017e-09
> > 4 p3 -5.79772e+03 4.44730e+00 2.76457e-03 9.71526e-09
> > 5 p4 1.94450e+03 3.58314e+00 1.54134e-03 6.48922e-08
> >
> > -it fits parameter 0 though claiming it is fixed!?
> >
> > -am I doing somthing real stupid or is this a bug?
> >
> > Art S.
> >
> > note a: "e" is the name I gave the TF1 function *efit. BTW, the function
> > TH1::Fit(TF1*) also seems to be missing in action, so I have to use the
> > one that finds the function by name rather than pointer.
> >
> > A.E. Snyder, Group EC \!c*p?/
> > SLAC Mail Stop #95 ((. .))
> > Box 4349 |
> > Stanford, Ca, USA, 94309 '\|/`
> > e-mail:snyder@slac.stanford.edu o
> > phone:650-926-2701 _
> > http://www.slac.stanford.edu/~snyder BaBar
> > FAX:650-926-2657 Collaboration
> >
> > On Sun, 2 Dec 2001, Rene Brun wrote:
> >
> > > Art,
> > >
> > > Even in PAW, people included the Minuit commands in a KUIP macro.
> > > You should do the same. However, currently, it is not easy to get
> > > the control after each iteration. You get the control only at the end
> > > of the fit, unless you implement your own fitting model (like
> > > H1FitChisquare or likelihood). One could imagine a new option
> > > to force a call to a function or macro after each iteration.
> > > If there are more suggestions, they are welcome.
> > >
> > > Rene Brun
> > >
> > > On Sun, 2 Dec 2001, Arthur E. Snyder wrote:
> > >
> > > > Hi Rene,
> > > >
> > > > I was able to grab gMinuit and use mnexcm to execute minuit commands, refit,
> > > > etc. It is pretty awkward interactively, but works. However, the results do
> > > > not propagate back to the function attached to my histogram, so when I
> > > > redraw it I see the result of the original default fit. Also, if I refit it
> > > > seems to start again from scratch and forget any 'fix' or 'set par' I've
> > > > done to gMinuit object.
> > > >
> > > > Perhaps, I would be better off using the get/set functions provided in TF1?
> > > > It looks pretty easy to write my own little macro to manipulate these
> > > > functions with minimal typing ...
> > > >
> > > > Art
> > > >
> > > >
> > > > ----- Original Message -----
> > > > From: "Rene Brun" <brun@pcbrun.cern.ch>
> > > > To: "Arthur E. Snyder" <snyder@SLAC.Stanford.EDU>
> > > > Cc: <roottalk@pcroot.cern.ch>
> > > > Sent: Sunday, December 02, 2001 1:39 PM
> > > > Subject: Re: [ROOT] Interactive minuit access from ROOT?
> > > >
> > > >
> > > > > Use the global gMinuit
> > > > >
> > > > > Rene Brun
> > > > >
> > > > > On Sun, 2 Dec 2001, Arthur E. Snyder wrote:
> > > > >
> > > > > > Thanks, Rene. Can you tell me how I access TMinuit object when I'm
> > > > fitting a
> > > > > > histogram? I don't find an assessor either in TF1 or TH1. I've also
> > > > looked
> > > > > > up the inheritance tree but don't find anything that looks like the
> > > > right
> > > > > > thing.
> > > > > >
> > > > > > Art
> > > > > >
> > > > > >
> > > > > >
> > > > > > ----- Original Message -----
> > > > > > From: "Rene Brun" <brun@pcbrun.cern.ch>
> > > > > > To: "Arthur E. Snyder" <snyder@SLAC.Stanford.EDU>
> > > > > > Cc: <roottalk@pcroot.cern.ch>
> > > > > > Sent: Sunday, December 02, 2001 9:49 AM
> > > > > > Subject: Re: [ROOT] Interactive minuit access from ROOT?
> > > > > >
> > > > > >
> > > > > > > Hi Art,
> > > > > > >
> > > > > > > The direct equivalent of PAW option "M" does not exist.
> > > > > > > However, you can invoke any function from TMinuit directly.
> > > > > > > This should provide even more flexibility at the expense
> > > > > > > of slightly more typing.
> > > > > > >
> > > > > > > Rene Brun
> > > > > > >
> > > > > > > On Sat, 1 Dec 2001, Arthur E. Snyder wrote:
> > > > > > >
> > > > > > > > Try again to post this with more sensible subject line!
> > > > > > > >
> > > > > > > > ----- Original Message -----
> > > > > > > > From: "Arthur E. Snyder" <snyder@SLAC.Stanford.EDU>
> > > > > > > > To: <roottalk@pcroot.cern.ch>
> > > > > > > > Sent: Saturday, December 01, 2001 12:29 AM
> > > > > > > > Subject: Re: [ROOT] tiny Bug in root
> > > > > > > >
> > > > > > > >
> > > > > > > > > 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
> > > > > > > > >
> > > > > > > > >
> > > > > > > > >
> > > > > > > >
> > > > > > > >
> > > > > >
> > > >
> > >
>
This archive was generated by hypermail 2b29 : Tue Jan 01 2002 - 17:51:10 MET