[R] distribution freq

catalin roibu
Fri, 26 Feb 2016 15:08:58 -0000

Thank you very much for your response.

But the problem still remained. I obtained my distribution parameters for
all diameter data (without lump).I sow that you create the fitted freq
using a difference from the neighborhood classes  (8-4), but I have a huge
interval from 96 fo 4. If I put diff(pgamma(c(96,8), shape, rate)) I
obtaining the same values for all classes.

Thank you very much for your help!

Best regards!


On 26 February 2016 at 14:41, Duncan Murdoch <murdoch.duncan at gmail.com>
wrote:

> On 26/02/2016 4:09 AM, catalin roibu wrote:
>
>> I'm working in forestry research and need the fitting distribution
for
>> forest structure in relation with diameter.
>> The tree diameter have been lumped into 4 cm diameter classes, forming
the
>> diameter experimental distribution.
>> For fitting I used the gamma distribution and I obtained the
distribution
>> parameters (scale and rate). After that I used the dgamma function and
I
>> have the pdf values. My question is how to obtain fitted absolute
>> frequency
>> to compare with the true frequency?
>>
>
> Since you're lumping into classes, you don't want the density, you
want
> differences in the cumulative probability.  So if your class runs from 4 to
> 8 cm, use something like
>
> pgamma(8, shape, rate) - pgamma(4, shape, rate)
>
> or the equivalent but a little obscure
>
> diff(pgamma(c(8, 4), shape, rate))
>
> Duncan Murdoch
>
> P.S. Please keep discussion on the mailing list.  I've cc'd this
response
> there.
>
>
>


--

-
-
Catalin-Constantin ROIBU
?
Lecturer PhD, Forestry engineer
Forestry Faculty of Suceava
Str. Universitatii no. 13, Suceava, 720229, Romania
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