[R-sig-Geo] ReadShapePoly subsetting data

[Peter Larson]

Hello all,

I have data for several states and no data for most. I just want to 
subset the states I have data for and ignore the rest.

Is there anyway to do this? I have a shapefile and have read it in with 
ReadShapePoly successfully, but I don't need all 50 American states.

Thanks,

Pete