[R-sig-Geo] Method for: Creating contour maps of geocoded point shapefile attributes

[Rick Reeves]

Hello:

If one has a polygon shapefile of the USA and a point shapefile of USA 
cities (both in geographic coordinates),
and the point shapefile includes demographic attributes for each city, 
what would be the best way to create
a contour map of one of the attributes that overlays the polygon map?

I have been experimenting with using akima.interp (to generate a grid of 
interpolated values) and contour (to
generate the contours), with mixed results. I think that I can work out 
a technique to get this done, but would
like to know if this capability is embedded in any of the R spatial 
classes.

Thanks for any insight into this!

Rick Reeves
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