[R-sig-Geo] Quickest way to tell if an arbitrary file is a raster/vector?

[Jonathan Greenberg]

r-sig-geo'ers:

I'm working on a GIS cataloging function to add-in to spatial.tools, and
one thing I'm struggling with is the quickest way to tell if a given file
is a GDAL/OGR readable raster/vector.  Any ideas?

--j

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