Re: [R] Plotting Bi-Gamma Distribution

From: Ben Bolker <bolker_at_ufl.edu>
Date: Wed, 02 Jul 2008 12:17:53 +0000 (UTC)

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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