[R] predict.glm and predict.gam output

[Anke Konrad]

Hi all,

I am currently trying to compare different plant occurrence prediction 
maps generated in R and exported into GRASS. One of these maps was 
generated from a glm fitted to some data, and subsequently applying this 
glm model to a wider region using predict.glm. The outcome here was a 
probability of occurrence. The second map I generated using a gam 
(mgcv), however, this map seems to have assigned something like a 
negative log-likelihood of occurrence to each raster cell in the region. 
Since I would like to compare the two, I would like to figure out a way 
of having the same kind of output from the "predict" functions (either 
probability OR negative log-likelihood). Does anyone know of a way of 
changing the output options? And if not, does anyone have any 
suggestions of how I could deal with this issue?

Thank you!