[SciPy-user] optimize.leastsq

josef.pktd@gmai... josef.pktd@gmai...
Thu Jan 22 09:47:46 CST 2009


On Thu, Jan 22, 2009 at 10:03 AM, David Trethewey <dlrt2@ast.cam.ac.uk> wrote:
> Managed to get this working with my data. Being able to do a 2-d fit
> with both metallicity and velocity information used is certainly
> interesting, although it doesn't seem to be too good at detecting
> subpopulations within my stellar stream which is what I'm trying to do.
>

>From my experience with hidden Markov models (estimated with ML not
EM), I know that good starting values for the location parameters are
necessary to get reliable results. I think, that the global properties
of the likelihood function are not very "nice".

What are you using as starting values?
I would try to get the suspected number of clusters and cluster
centers from visual inspection of the 2D histogram (or from stats.kde)
and use these as starting values.  The variance I would set so that
initially the individual distributions have only a small overlap.

Josef


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