Re:

From: Rene Brun (Rene.Brun@cern.ch)
Date: Wed Nov 17 1999 - 08:33:59 MET


Hi Franck,
Thanks for reporting this interesting problem and the example.
This was a problem in TGraph::Fit when computing the initial values
for the parameters in case one fits in a sub-range of a graph.
I have fixed the problem in my development version 2.23/09.

Rene Brun


LAVAUD FRANCK wrote:
> 
>         Hello,
> 
>         I have a problem with FIT. I have written a very simple program
> to show you my problem: I considere 3 points: (x1,y1) (x2,y2) (x3,y3),
> and I fit with the 'pol1' on the interval x1 to x2 and with a other 'pol1'
> on the interval x2 to x3. In fact, It is very easy to find the solution
> (y=ax+b, then a=(y2-y1)/(x2-x1) and b=y2-a*x2=y1-a*x1) but Root don't
> arrive to find the good solution! I don't understand why it is a problem.
> It is may be a problem in my program but, if it is this case, I don't
> know where!
> 
>         Thank you by advance,
> 
>                                                 Franck Lavaud
> 
> NB: I use root 2.23
> 
> -----------------------------------------------------------------------
> 
>                            LAVAUD FRANCK
> 
>                Institut de Physique Nucleaire - Bat. 102
>                        Universite de Paris-Sud
>                          F91406 ORSAY Cedex
> 
>      Tel.: (33) 01.69.15.72.43        E-Mail: Lavaud@ipno.in2p3.fr
>                                               Lavaud@in2p3.fr
> 
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