I have no trouble importing a subset of a road network for my study area as
a shapefile into R, but when I try to import the complete network (area
equivalent to approximately 30,000 km^2), I get the following error message
(even when I split up the two class formats into two separate commands):

> fullroads<-as(as(readShapeLines(fn="D:\\GIS\\roadnet.shp"),
"SpatialLines"), "psp")
*Error in function (classes, fdef, mtable)  :
  unable to find an inherited method for function "coordinates", for
signature "numeric"*
**
Is this due to the memory limitations of R, or to those of my particular
machine, or to something else I'm missing?  The processes I am trying to
model are happening at very "large" spatial scales and it would be a great
deal more efficient if I could use the entire road network rather than
dealing with multiple subsets of a greater image.  Importing as an ascii
grid is not an option due to subsequent operations using distmap() which are
based on the psp format.

Tyler

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