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.
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