[R-sig-Geo] Re: [R] A package for spatial data classes: request for comments
Edzer J. Pebesma
e.pebesma at geog.uu.nl
Mon Nov 3 16:08:17 CET 2003
Barry Rowlingson wrote:
>> To be really useful, the class should include vector (polygon) data,
>> and probably line elements. For this, I need help. The simples approach
>> would be to extend SpatialDataFrame to SpatialDataFramePolygon,
>> and add for each row add the corresponding polygon.
> I think you need to stop thinking about building classes at the
> moment, and to think about specifying _interfaces_. What methods do we
> want for spatial data? How will functions get the spatial data out of
> the objects? Then we can build classes that implement these interfaces.
Baz, I agree that interfaces are important. Still, concentrating on
does encourage package writers to come up each with a new set of spatial
-- something I would like to discourage: sharing more code makes the
I did build upon your idea of sp.coords, but called it coordinates, and
used reference (column name/numbers) instead of actual values:
coordinates(meuse) = c("x", "y")
I prefer coordinates because at some stage the S3 method mechanism may
interpret sp.coords as an sp method for a coords class.
My question, in your perspective, would be: which methods do we need for
a generic class containing vector/polygon data?
E.g. how is,
polygons(world) # gets or sets the polygons, as a list of 2 col matrices
polygonAttributes(world) # gets or sets the polygon attributes, as data
More information about the R-sig-Geo