[R] warning in binomial analysis

[Ronaldo Reis Jr.]

Hi,
I have make an analise with presence and absence, y=(1 e 0).
I have a area continuous data and a sp data with 25 levels. I have 300 points.
When I make

glm((presenca/peso)~area,weights=peso,family=binomial,maxit=1000)

where 

presenca is 0 or 1.

peso is the unit = 1.

area is the continuous data.

The analysis is OK.

When I put the sp and interactions in analysis this warning appear.

glm((presenca/peso)~area*sp,weights=peso,family=binomial,maxit=1000) 

Warning message:  

fitted probabilities numerically 0 or 1 occurred 

in: (if (is.empty.model(mt)) glm.fit.null else 

glm.fit)(x = X, y = Y,

Some ideas???

Thanks
Ronaldo

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