[R] Goodness of fit test for count data

pinusan anhong at msu.edu
Mon Feb 22 20:11:20 CET 2010

Dear  all, 

I am trying to test goodness of fit. I assume that a data follow Poisson or
Negative binomial distribution. I can test the goodness of fit in case of no
truncated data. However, I could not find any good function or packages when
a data is truncated.  

For example, a frequency table for the number of visiting emergency room in
one hundred one observations past one year is as follow: 
N freq 
1 30 
2 35 
3 26 
4 8 
5 0 
6 2 
7 0 

 I expect the frequency table to satisfy a Poisson distribution or Negative
binomial distribution. However, the distribution is different from the usual
Poisson or Negative binomial distribution because one value, zero, is
excluded. I expect that the distribution is zero truncated distribution. 

In case of SAS, I used NLMIXED procedure to calculate the expected
probability when y=1 … y=n under the assumption that a data follows Poisson
or Negative binomial distribution. And then I run Chi-square test. If you
need the SAS code, I will send E-mail.
I want to run this test in R.
Could you suggest any idea that can I perform this test in R.

Have a nice day.

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