[R] Plotting Bi-Gamma Distribution

[Wolfgang Raffelsberger]

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 <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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>> and provide commented, minimal, self-contained, reproducible code.
>>
>>     
>> ------------------------------------------------------------------------
>>
>> ______________________________________________
>> R-help at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>     


 
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Wolfgang Raffelsberger, PhD
Laboratoire de BioInformatique et Génomique Intégratives
CNRS UMR7104, IGBMC 
1 rue Laurent Fries,  67404 Illkirch  Strasbourg,  France
Tel (+33) 388 65 3300         Fax (+33) 388 65 3276
http://www-bio3d-igbmc.u-strasbg.fr/~wraff
wolfgang.raffelsberger at igbmc.fr