[R-sig-Geo] different models

[Virginia Morera Pujol]

Hi all,

This might be a very dumb question that shows I have very little idea of
what I am talking about, but I'll risk it:

What is the difference between fitting a model using these 3 different
syntaxes?

1/ fit1 <- ppm(ppp, ~covariate),
2/ fit2 <- ppm(ppp, ~x+y+Z, covariates=list(Z=covariate))
3/ fit3 <- ppm(ppp, ~x+y+covariate)

where ppp is my point pattern and "covariate" is a pixel image? I realise
the outputs of 2 and 3 are the same and different to that of 1, so I guess
the question really is

a/ Is there any difference, practical or in the actual computations of the
model, between using 2 and 3?
b/ What is the difference between (2&3) and 1?

Thanks a lot,

Virginia Morera
PhD Student
Department of Animal Biology
University of Barcelona

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