On Fri, 27 Oct 2006, Duncan Golicher wrote:
I have quite a number of SpatialGridDataFrame objects that were saved
internally under R 2.3.0 and sp0.8-16. Can anyone suggest a quick and
easy way to convert them for use with R2.4.0 and sp0.9-2. (I do have
ways, but they are all a bit longwinded).
The issue was announced on this list on 28 September:
https://stat.ethz.ch/pipermail/r-sig-geo/2006-September/001354.html
and has been on the Rgeo site since about the same time.
The major issue is that the way new-style classes (and objects belonging
to those classes) are defined internally, so the internal (*.RData)
representations are not compatible.
To transfer from the old internal form, use R < 2.4.0, and sp < 0.9 to for
example export column by column to GRASS, and then read back in in R >=
2.4.0 and sp >= 0.9. Alternatively for non-GRASS users, rgdal and the
GTiff fotmat could be used (and should work with multiple bands). The
writeAsciiGrid() function in maptools could also be used. There is no way
of upgrading the serialised object from the *.RData form directly.
We know that this is an unfortunate incompatibility, but the changes in
the methods package are being made to improve class/object handling,
making the software faster and more robust, so the difficulties are
unavoidable. For critical projects already using R < 2.4.0, I suggest only
upgrading when sensible.
Roger