Re: Problem with fitting
- To: mathgroup at smc.vnet.net
- Subject: [mg101551] Re: Problem with fitting
- From: dh <dh at metrohm.com>
- Date: Fri, 10 Jul 2009 06:42:43 -0400 (EDT)
- References: <h2fe8l$pvp$1@smc.vnet.net>
Hi Chris,
it looks like your expression does not depend on the parameter.
Try e.g.:
FindFit[Table[i, {i, 8}], x, {{a, 3}}, x]
and you get the message you describe.
Daniel
Chris Schreiber wrote:
> Hi there,
>
> I encounter the following problem when fitting a complicated function using FindFit: when running
>
> BBWorigin =
> FindFit[Data2, {CHFSorigin[x] /. ABWorigin /. ABW /. BBW /. CBW /.
> DBW /. FGW} , {{COorigin, 4.3}}, {x}, MaxIterations -> 1000]
>
>
> where I previously defined the function CHFSorigin and where the rules ABWorigin, ABW, BBW, CBW, DBW and FGW were also defined, I obtain the following output by mathematica:
>
> {COorigin -> 4.3}
> FindFit::fmgz: Encountered a gradient that is effectively zero. The \
> result returned may not be a minimum; it may be a maximum or a saddle \
> point. >>
>
> My first reaction was to change COorigin to a different value, but that did not change the result, i.e. the fit always stopped at the initial value. Does anybody have
> any ideas about how to progress from here?
>
> Best wishes, and thanks a lot,
>
> Christian
>