[R-sig-Geo] ring not closed - readShapePoly - read.shape - maptools

Patrick Giraudoux patrick.giraudoux at univ-fcomte.fr
Thu Dec 28 16:33:17 CET 2006


I have slept on some data of a project which started in 2003 and  just 
coming back on them today gives the opportunity to compare read.shape 
(shapefiles were initially imported with this function) and 
readShapePoly (the new one sp style). The latter will be much more 
interesting for the next step, giving directed handling to overlay methods.

Importing one of my shapefile with read.shape ( read as polyshape in 
ArcGIS) made (and still makes) no problem. However, when I try to import 
it again via readShapePoly, I get this message:

 > UG<-readShapePoly("U:/Documents and Settings/giraudoux/Mes 
Error in validityMethod(object) : ring not closed

Clear enough: at least one of the polygons is not closed... which is 
confirmed by the fact that I can import the shapefile easy with 
readShapeLines. I suppose the readShapePoly is more demanding in 
validity control than the older read.Shape and ArcGIS: one cannot 
complain for that.

I am not afraid of sorting this out with some lines of programme. I have 
however a question before writing it: is there already a function making 
a check somewhere which could be used to know which one(s) of the 
polygons are not closed?


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