Hi,
you can try the 'mixdist' package which allows fitting of multiple
(superposed) distributions to your vector of data.
The package is available on http://www.math.mcmaster.ca/peter/mix/mix.html
Unfortunately this package doesn't support combination of normal with
gamma etc..., but it could work for your case of 2 superposed gamma
distributions.
Wolfgang
Gundala Viswanath a écrit :
Hi Ben,
Thanks for the reply.
The gamma distribution is always unimodal (i.e.,
a single peak).
Unless I misunderstood you. I am thinking of mixture
of two gamma distributions. Attached paper maybe
interest. It discuss about such bimodal mixture of gamma distributions
(i.e. it exists).
I had a look at "mixtools" package
it has mixture modelling tools for almost all distributions
except Gamma :-(
- Gundala Viswanath
Jakarta - Indonesia
On Wed, Jul 2, 2008 at 9:17 PM, Ben Bolker <[EMAIL PROTECTED]> wrote:
Gundala Viswanath <gundalav <at> gmail.com> writes:
Hi all,
I've tried to plot a vector which has two peaks in the density.
This link shows the figure.
http://docs.google.com/View?docid=dcvdrfrh_1dk9r2rc7
The red line is normal curve and green line is gamma curve.
Notice that red line can correctly fit the histogram that has two peaks
(i.e. red curve also has two peaks).
But the gamma curve there only has one curve.
Is there a way I can fit the gamma function such that it also
yields two peaks?
The gamma distribution is always unimodal (i.e.,
a single peak). (You call the red line a "normal
curve", but it's really a nonparametric density
estimate.) You might want to search the list and
the available packages for "mixture models", which
are a standard way of fitting multimodal distributions ...
Ben Bolker
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