How to create polygons for kriging

-----Original Message-----
From: r-sig-geo-bounces at stat.math.ethz.ch
[mailto:r-sig-geo-bounces at stat.math.ethz.ch]On Behalf Of 
Chloe ARCHINARD
Sent: 17 May 2005 13:19
To: r-sig-geo at stat.math.ethz.ch
Subject: [R-sig-Geo] How to create polygons for kriging


Hello all,

I used geoR package to compute kriging with krige.conv() , 
and to draw map I used contour() like this :

contour(kc,locations, filled=TRUE, coords.data=geodata$coords,

+color=terrain.colors)

And I want to limit the prediction inside data locations 
(with borders()) which are not rectangular, so how can I 
create a polygon which could contain my data? Or if someone 
knows where I can find polygons data frame for the states of the US?