[R-sig-Geo] spatstat, maptools, sp, and as.ppp

[Mark Connolly]

I may be just dense, but maybe this will help someone else avoid some 
head-brick wall interactions.

If you just _know_ that yesterday you weren't getting "Error in 
as.ppp.default(varname) : Can't interpret X as a point pattern" when you 
were executing as.ppp on a SpatialPoints instance, then it may be that 
yesterday you were loading maptools and today you are not.