[R-sig-Geo] Please read before upgrading to R 2.4.0!

[Roger Bivand]

The release of R 2.4.0 is imminent, and will involve major changes in the 
handling of objects of classes defined in the sp package. Please make sure 
to export any objects you need to use to external files before upgrading 
to R 2.4.0, then upgrade and update packages. The 0.9-* series of the sp 
package are for R >= 2.4.0, 0.8-* for R <= 2.3.1. 

This warning applies to users who save sp objects using save() or 
save.image(), that is save them in their internal form. It is this form 
that is being changed because of improvements in the core methods package, 
so the advice given here is unavoidable. 

Since this incompatibility is happening anyway, we have taken the
opportunity of changing the representation of the data slot in
SpatialPointsDataFrame, SpatialPixelsDataFrame and SpatialGridDataFrame
objects from AttributeList to data.frame, because the handling of row
names in the R core data.frame object has been improved for objects with
many rows.

-- 
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: Roger.Bivand at nhh.no