Problem in converting SpatialPolygonsDataFrame to owin object
On Thu, 14 Sep 2006, Edzer J. Pebesma wrote:
Debarchana Ghosh wrote:
works fine; I modified the code such that
xx1<-as(xx, "owin")
will work fine as well in the future.
--
So I just download and install the updated spspatstat package?
I said "future", not "near future" or "now"; spspatstat isn't on CRAN. If you wish you could download the source from anonymous cvs on the r-spatial sourceforge project. It is not there where your problem is, however, as you were able to transform to SpatialPolygons anyway.
Also, I know attachment is not the right way to converse on this list-serve but I couldn't think of any other way to show my study area. So I've attached the image of my study area (polygon). As i've mentioned in my earlier email, I've read a shapefile in R and created a object (xx) of class SpatialPolygonDataFrame. Howver when I try to convert xx to owin I get the following error. As shown in the attachment, the lines do not intersect but has 7 contigous US counties. Any solution to this problem will be very helpful.
The problem may be that polygons are only slightly intersecting (which you cannot find out from a bitmap image), or that some code is making wrong assumptions. The error message comes from the owin function in the spatstat package. If the author of the package doesn't listen to this list, you could contact him directly (I Cc:d this message). To me, at first glance it looked like the error generating code is a fairly recent add to spatstat, but I may be wrong on that.
Is it possible to make the offending shapefiles available to me/others? Without them it is very difficult to debug - SpatialPolygons do not check for intersections. I would suggest using spgpc (also on sourceforge) to clean the polygons, but first we need to find out if they do intersect. Roger
-- Edzer
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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