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problem with csr {splancs}
2 messages · António M. Rodrigues, Roger Bivand
On Wed, 4 May 2011, Ant?nio M. Rodrigues wrote:
Hi,
I need to create a number of random points inside a polygon using car
{splancs}.
Let's say I have a SpatialPolygonsDataFrame with only one polygon, and I
want to throw 100 points inside randomly.
If the object is called poly1, I thought this would work:
csr(poly1,100)
?csr perhaps? "poly: A polygon data set", not a SpatialPolygons object. If you do: data(bodmin) str(bodmin$poly) you see that splancs, which is effectively unchanged since written almost 20 years ago, needs a two-column matrix. In your case, if poly1 is a SpatialPolygons object with a single Polygons object, which in turn has a single member Polygon object, the polygon for splancs would be: poly1pl <- slot(slot(slot(poly1, "polygons")[[1]], "Polygons")[[1]], "coords") Perhaps we should start planning for a birthday party for splancs, one of the real achievements in S/R and spatial statistics! Roger
But I get the error: Error in `[.data.frame`(x at data, i, j, ..., drop = FALSE) : undefined columns selected I thought this might have to do with the class, so I did:
teste <- slot(poly1,"polygons")
And tried
csr(teste,100)
Now I get: Error in poly[, 1] : incorrect number of dimensions I apologise if this is a very simple question. Thanks in advance, Ant?nio [[alternative HTML version deleted]]
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