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