R crash with readOGR
On Fri, 12 Feb 2010, caspar hallmann wrote:
Dear All,
Perhaps one can help me with the obvious, however I have been trying
to import a shapefile using function readOGR as in:
myshp<-readOGR("mydirectorypath", "shapefilename"), and without any
warning (e.g. can't allocate memory size or something trivial) R
crashes en shuts down. The shapefile itself does not seem too large
though ( 42mb the .shp alone).
OK. You are on Windows, where memory management is not as capable as on
Unix-based systems. If R say that it cannot allocate memory under Windows,
it has not "crashed", only responded to the inadequacy of the system. If
you read the R for Windows FAQ, you'll see some tricks for improving
memory use. A 42MB shapefile is very large, you have not said what you
need to use it for.
The R lists posting guide does say when you can term anything a crash,
this is not one of those cases.
There is no separate function for reading a *.prj file. The so-called WKT
spatial reference in the *.prj is read by the OGR driver, and converted to
PROJ.4.
"OGRSpatialRef" <- function(dsn, layer) {
.Call("ogrP4S", as.character(dsn), as.character(layer),
PACKAGE="rgdal")
}
is a function that will return that representation without trying to read
the features, I'll add it and one for GDAL rasters to the next release -
the GDAL information is already in the object returned by GDALinfo(), but
noy yet in that returned by ogrInfo().
Hope this helps,
Roger
I wonder if anyone has encountered the same problem, or beter, the solution. For now, I have resorted to importing the .dbf of the shapefile (works fine), then converting it to some preferred spatial format. However, since now I am required to manually set the CRS this pretty much prevents me from applying batch analysis on a range of shapesfile differing in their CRS's. Note that the .prj are present, and would like to take advantage of readOGR's capability of recognizing the CRS of each shapefile. Thanks in advance Caspar PS: BTW: Is there a function like ''readprj()'' around ? PS2: sessionInfo: R version 2.10.1 (2009-12-14) i386-pc-mingw32 locale: [1] LC_COLLATE=Dutch_Netherlands.1252 LC_CTYPE=Dutch_Netherlands.1252 LC_MONETARY=Dutch_Netherlands.1252 LC_NUMERIC=C [5] LC_TIME=Dutch_Netherlands.1252 attached base packages: [1] stats graphics grDevices utils datasets methods base other attached packages: [1] RSAGA_0.9-6 rgdal_0.6-24 maptools_0.7-29 lattice_0.18-3 sp_0.9-57 foreign_0.8-39 loaded via a namespace (and not attached): [1] grid_2.10.1 proj4_1.0-4 tools_2.10.1
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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