[R] calculating goodness-of-fit statistics

From: Taka Matzmoto <sell_mirage_ne_at_hotmail.com>
Date: Wed 01 Feb 2006 - 13:03:25 EST


Hi R users

I have a simple data for calculating goodness-of-fit statistics (e.g., X2 by Pearson, G2 by Wilks)

#################################################
observed<-c(424,174,0,402)
expected<-c(282.7174, 314.2972, 142.3142, 260.6712) 2*sum(observed*log(observed/expected)) # for X2 sum((observed-expected)^2/expected) # for G2
#################################################

(note. expected ones were calculating by a model I used, not by marginal of observed ones.)

The third element of the observed vector is zero.

For third element, 0 * log(0/142.3142) is NaN. That is why I got NaN for G2.

I think 0 multiplied by anything should be zero. Am I wrong ?

Is there any R functions to correct zero cells for calculating G2? If there is, I like to know some

references justifying the correction.

Thank you in advance

TM



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