[R-sig-Geo] Changes in the sp package

[Roger Bivand]

A number of changes have been made in the sp package which may affect 
users. Version 0.9-56 is now on CRAN and is the first release containing 
the changes.

The changes involve the creation of Polygon, Polygons, and SpatialPolygons 
objects in C rather than R code, and in the exposure of these C functions 
to other packages (less important for now). I see speedups of about four 
times in reading large polygon shapefiles in readOGR() in rgdal, and 
similarly in readShapeSpatial() in maptools (which remains slower), 
because the sp instantiation functions called there also call the C 
functions inside sp.

They have been tried out following an announcement on this list last 
month:

https://stat.ethz.ch/pipermail/r-sig-geo/2009-December/007224.html

with no significant problems reported. The only visible change appears to 
be the names of the dimensions in the bounding box of SpatialPolygons 
objects, which now are c("x", "y").

Thanks to Micah Altman, the "[" subsetting method for 
SpatialPolygonDataFrame objects has also been speeded up, again by about 
4x - this does not involve C code.

If changes are noticed, please contact me directly with a reproducible 
example.

Thanks in advance for your cooperation,

Roger

-- 
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