[R] Using GIS data in R

[Rolf Turner]

On 21/11/11 10:19, Zuofeng Shang wrote:
> Hi Rolf,
>
> Thanks very much for suggestions! Sorry if I made my question not very 
> clear.
>
> The context is as follows. I have a set of locations with coordinates 
> (latitude and longitude)
> from Texas region. Some of the locations are within Texas while some 
> of them are not.
> I am trying to find those locations within Texas by looking at if the 
> coordinate of each location
> is within the boundary of Texas.
>
> Now I agree with you that the boundary of Texas is polygon although it 
> looks like "irregular".
> I find your previous post very helpful. inside.owin() will do the job 
> but I have to figure out
> the boundary (as a polygon) of Texas. Since I do not have the 
> shapefile of Texas, this will be
> difficult for me. I am not sure if the shapefile of the US states are 
> available in R. If it not,
> how can I get the shapefiles? Thanks a lot for kind help!

This is not my area of expertise (if indeed I have such an area at all! 
:-) ) but
I'm sure that maps of the states of the USA --- including Texas, even! 
--- are readily available
from various sources.  I.e. from various GIS's or perhaps from the 
"maps" package.

With a bit of luck someone on the list will chime in with something more 
specific.

Or you could try asking "how/where can I get a shapefile specifying the 
boundary
of Texas" on the R-Sig-Geo list.

HTH

     cheers,

         Rolf