You can compute the conditional probability that your variable equals k given that it is non-zero. For example, if X has poisson distribution with parameter lambda then P(X=k/X!=0) = P(X=k)/(1-P(X=0)) = (exp(-lambda)/(1-exp(-lambda))*lambda^k/k! Now you can find lambda for which the sum of squares of your errors is minimal and then use CHi-aquared test using these expected frequencies.
Similarly for negative binomial distribution. --- On Tue, 23/2/10, pinusan <anh...@msu.edu> wrote: > From: pinusan <anh...@msu.edu> > Subject: [R] Goodness of fit test for count data > To: r-help@r-project.org > Received: Tuesday, 23 February, 2010, 6:11 AM > > 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. > > -- > View this message in context: > http://n4.nabble.com/Goodness-of-fit-test-for-count-data-tp1564963p1564963.html > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > R-help@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. > ______________________________________________ R-help@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.
