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!
Best regards,
Jeff
On 21/11/11 08:01, JeffND wrote:
Hi Rolf,
I have a similar question. I want to test whether a point with certain
coordinates is inside
a state, say Texas. It seems that inside.owin() only works for testing if a
point lies in a
regular region, say a polygon. Since Texas has irregular boundary, how do we
achieve this?
Or there is some alternative way we can use.
Thanks!
Jeff
--
View this message in context:
http://r.789695.n4.nabble.com/Using-GIS-data-in-R-tp1748266p4089242.html
Sent from the R help mailing list archive at Nabble.com.
It would be nice to have some context ... nabble strikes again.
But to get to your question: How do you think the boundary of Texas
(irregular as it may be) is specified? I expect that it is specified as
a polygon!!! It may be *very* ``poly'' --- i.e. have a large number of
edges --- but it's still a polygon and inside.owin() will still work on it.
Have a look at the data set "nbfires" in the spatstat package. New
Brunswick has an ``irregular boundary'' too!
Have you *tried* making your specification of Texas into an owin object?
Follow the instructions in the vignette given by:
vignette("shapefiles")
cheers,
Rolf Turner
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