[Insight-users] itkExpectationMaximizationMixtureModel
ahmad bukhari
highway_111@mail.com
Mon, 28 Oct 2002 07:46:42 -0500
hi jisung and others...
The assignment of weightages is global and hence it shall not be effective
..In a certain intensity zone a class may not be present at all and then
assigning weightages does not help in any way....
An example of adding a component shall be useful for me.
thanks
ahmad
----- Original Message -----
From: Jisung Kim <bahrahm@yahoo.com>
Date: Fri, 25 Oct 2002 07:11:31 -0700 (PDT)
To: ahmad bukhari <highway_111@mail.com>, insight
<insight-users@public.kitware.com>
Subject: Re: [Insight-users] itkExpectationMaximizationMixtureModel
> Hi ahmad,
>
>
> --- ahmad bukhari <highway_111@mail.com> wrote:
> > hi everyone!!
> > There is another issue that i need help with:
> > the mixture model can finally give you an estimate
> > of
> > the different classes presence....but the trouble is
> >
> > that different classes occur in different intensity
> > regions. For example in an intensity zone on a
> > typical
> > frequency histogram plot different classes occur in
> > different regions interfering in some cases and
> > isolated
> > in rest. So the mixture model perhaps should be
> > applied
> > (initialized)differently for different intensity
> > zones
> > to get an accurate picture. Is there a way out...??
>
> Each iteration of the EM estimation process updates
> weights for measurement vectors with given
> "components". In other words, in the test program,
> each measurement vector has two weight values that
> tells you how likely the measurement vector belongs to
> the two Gaussian classes. When the Gaussian components
> update their parameters, they use the weights instead
> of using simple mean and covariance calculations. This
> weighted mean and weighted covariance calculations
> actually has similar effect that you mentioned. If a
> measurement vector highly likely belong to a component
> (let's say component A) but not to the other
> component (component B), then the measurement vector
> will affects the parameter calculation of component A
> but won't affect much that of component B.
>
> Is this what you need?
>
>
>
> > thanks
> > ahmad
> > --
> >
>
> Thanks,
>
> Jisung.
>
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>
> =====
> Jisung Kim
> bahrahm@yahoo.com
> 106 Mason Farm Rd.
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