[R] Goodness of fit to Poisson / NegBinomial

[Mark Myatt]

All,

I have some data on parasites on apple leaves and want to do a
goodness of fit test to a Poisson distribution. This seems to
do it:

  mites <- c(rep(0,70),
             rep(1,38),
             rep(2,17), 
             rep(3,10), 
             rep(4,9), 
             rep(5,3), 
             rep(6,2), 
             rep(7,1))

  tab <- table(mites)
  NSU <- length(mites)
  N <- sum(mites)
  NSU.Mean <- N / NSU
  exp <- dpois(as.numeric(dimnames(tab)[[1]]), NSU.Mean) *  NSU
  chi2 <- sum(((as.vector(tab) - exp)^2) / exp)

  tab
  exp
  chi2
  
I have some small expected values and so need to collapse some
categories. If anyone has code to do that already ... but my
question is how would I do the same for a negative binomial
distribution?

Mark

--
Mark Myatt


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