On Thu, Nov 4, 2010 at 10:25 AM, Edzer Pebesma
<edzer.pebe...@uni-muenster.de> wrote:
> Because the documentation sais so. ?writeOGR tells me:
>
> Usage:
>
> writeOGR(obj, dsn, layer, driver, dataset_options = NULL,
> layer_options=NULL, verbose = FALSE)
>
> Arguments:
>
> obj: a SpatialPointsDataFrame, SpatialLinesDataFrame, or a
> SpatialPolygonsDataFrame object.
Although that's not what the code says:
if (!"data" %in% names(getSlots(class(obj))))
stop("obj of wrong class")
- it just looks to see if there's a 'data' slot in the argument, and
then carries on, stumbling blindly into all sorts of problems if one
is dumb enough to create a class with a data slot:
> setClass("foo",representation(data="numeric"))
> z=new("foo")
> writeOGR(z,dsn="/tmp",layer="pts",driver="ESRI Shapefile")
Error in writeOGR(z, dsn = "/tmp", layer = "pts", driver = "ESRI Shapefile") :
NULL NULL unknown data type
Surely there should be _methods_ for writeOGR for classes that it
supports, such as SpatialPointsDataFrame. Explicitly testing for the
presence of a slot/member is worse than explicitly testing for the
name of a class when you should really use 'inherits' which is worse
than the correct approach which is writing methods...
*end mini-rant* :)
Barry
_______________________________________________
R-sig-Geo mailing list
R-sig-Geo@stat.math.ethz.ch
https://stat.ethz.ch/mailman/listinfo/r-sig-geo
