[R-sig-Geo] Problem reading in polygon shapefile with readShapePoly

[Roger Bivand]

On Mon, 22 Jun 2009, Steven J. Pierce wrote:

> Hi folks,
>
> I've been trying to read a polygon shapefile I received from an ArcGIS user
> into R with the tools provided in the maptools and rgdal packages. When I
> tried reading in a file with boundaries for parcels of land, I get an error
> message that reads "Error in from[j]:to[j] : NA/NaN argument" and the
> parcels object is not created. This is similar to a situation recently
> discussed on this list (on June 10th), so I tried adding the option
> delete_null_obj=TRUE to the readShapePoly() command, but then just get a
> different error message after doing that and the object still does not get
> created. Based on the mention of rings not being closed in the new error
> message, I took a guess that maybe adding force_ring = TRUE would help, but
> that also has not solved the problem. The parcels object is still not being
> created.
>
> The shapefile seems to work just fine in ArcGIS and as part of a published
> map I can open in ArcReader.  In fact, I've got access to couple different
> parcel shapefiles and all of them generate this error, whereas all the other
> polygon shapefiles I've got access to (e.g., Census block boundaries) work
> just fine. I'd really like to get this parcel shapefile imported into R and
> stored as a SpatialPolygonsDataFrame object, so I would appreciate any
> insight you can provide on what's going wrong or suggestions on how to
> diagnose and fix the problem, whether it that requires changing my code, or
> even modifying the shapefile back in ArcGIS.
>
> Below is an excerpt from my console, with traceback() and sessionInfo()
> output at the end.

Thanks for a full report. What this is saying is that there are both 
NULL geometries that are being removed, and in addition there appear 
to be non-closed rings even when the force_ring policy is being used.

Without access to the file, I'm afraid that finding a solution is not 
feasible. If you can zip the parcel_mast_20050802.* files (and possibly 
others with the same problem) and put them online, and send me the URL 
off-list, or attach the zip archive if < 2MB, I'll have a look. I have an 
as-yet unreleased version of maptools that may be able to handle this 
case, but seeing the offending files would be very useful.

Hope this helps,

Roger

>
>> parcels <- readShapePoly("Parcels Shapefile/parcel_mast_20050802.shp",
> +                        proj4string = CRS(parcels.proj4), verbose=TRUE,
> +                        delete_null_obj=TRUE, force_ring=TRUE)
> Shapefile type: Polygon, (5), # of Shapes: 21842
> Error in validityMethod(object) : ring not closed
> In addition: Warning message:
> In .Map2PolyDF(Map, IDs = IDvar, proj4string = proj4string, force_ring =
> force_ring,  :
>  Null objects with the following indices deleted: 8519, 9096, 9528, 13665,
> 15880
>> traceback()
> 13: stop("ring not closed")
> 12: validityMethod(object)
> 11: identical(x, TRUE)
> 10: anyStrings(validityMethod(object))
> 9: validObject(.Object)
> 8: initialize(value, ...)
> 7: initialize(value, ...)
> 6: new("Polygon", sl, labpt = cG$cents, area = cG$area, hole =
> as.logical(hole),
>       ringDir = as.integer(rD))
> 5: Polygon(coords = crds)
> 4: .shp2srsI(shapes[[belongs[[i]][j]]],
> .nParts.shpI(shapes[[belongs[[i]][j]]]),
>       force_ring = force_ring)
> 3: .asSpatialPolygonsShapes(Map$Shapes, IDs, proj4string = proj4string,
>       force_ring = force_ring)
> 2: .Map2PolyDF(Map, IDs = IDvar, proj4string = proj4string, force_ring =
> force_ring,
>       delete_null_obj = delete_null_obj, retrieve_ABS_null =
> retrieve_ABS_null)
> 1: readShapePoly("Parcels Shapefile/parcel_mast_20050802.shp", proj4string =
> CRS(parcels.proj4),
>       verbose = TRUE, delete_null_obj = TRUE, force_ring = TRUE)
>> is.projected(parcels)
> Error in extends(class(sd), "Spatial") : object 'parcels' not found
>>
>> sessionInfo()
> R version 2.9.0 (2009-04-17)
> i386-pc-mingw32
>
> locale:
> LC_COLLATE=English_United States.1252;LC_CTYPE=English_United
> States.1252;LC_MONETARY=English_United
> States.1252;LC_NUMERIC=C;LC_TIME=English_United States.1252
>
> attached base packages:
> [1] stats     graphics  grDevices utils     datasets  methods   base
>
> other attached packages:
> [1] spatstat_1.15-3 deldir_0.0-8    gpclib_1.4-4    mgcv_1.5-5
> [5] rgdal_0.6-8     maptools_0.7-23 sp_0.9-37       foreign_0.8-36
>
> loaded via a namespace (and not attached):
> [1] grid_2.9.0      lattice_0.17-25 nlme_3.1-92
>
>
> Steven J. Pierce
> Center for Statistical Training & Consulting (CSTAT)
> Michigan State University
> Web: http://www.cstat.msu.edu
>
>
>
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>
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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