nobs() and logLik()

G'day Brian,

On Fri, 20 Jan 2012 06:20:30 +0000

I do wonder why people use zero weights rather than 'subset', and I 
don't particularly like the discontinuity as a weight goes to zero.

I completely agree, and for developers it is a bit of a pain to make
sure that all possible combinations of 'subset' and 'weights' play
"nicely" together.

One reason that I can see for people to use zero weights rather than
'subset' is that fitted() and predict() in the former case readily
produce fitted values for the observations that received a zero weight.

Cheers,

	Berwin