Re: [R] Plotting Bi-Gamma Distribution

From: Gundala Viswanath <gundalav_at_gmail.com>
Date: Wed, 02 Jul 2008 22:52:16 +0900

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 :-(

On Wed, Jul 2, 2008 at 9:17 PM, Ben Bolker <bolker_at_ufl.edu> 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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Received on Wed 02 Jul 2008 - 13:57:21 GMT

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