Karen,
you could try converting your polygons to raster using rasterize() in the
raster library, and then use the extract() function to retrieve the cell
values corresponding to your XY locations. I've used this workaround for
similar problems in the past.

Zack



On Thu, May 23, 2013 at 9:00 AM, karengrace84 <kgfisher@alumni.unc.edu>wrote:

> I am new to mapping with R and having some trouble. Here is what I am
> trying
> to accomplish. I am looking at fish tagging data. I have gps coordinates of
> where each fish was tagged and released, and I have a map of 10 coastal
> basins of the state of Louisiana. I am trying to determine which basin each
> fish was tagged in, so that I can perform further analysis from there.
>
> I've used the sp and rgdal packages to input my shp files of the coastal
> basins, and I have my list of gps coordinates where the fish were tagged.
> I've tried using the point.in.polygon() function and the over() function
> from the sp package unsuccessfully. Can someone please tell me how to use
> one of these functions correctly, or if there is a better way to reach my
> goal?
>
> For the point.in.polygon() function, I am unsure of how to get my data in
> the correct format for the function. The generic form of the function is as
> follows:
>
> point.in.polygon(point.x, point.y, pol.x, pol.y, mode.checked=FALSE)
>
> I have no problem with the point.x and point.y inputs. My problem is with
> the pol.x and pol.y input. My polygon is currently in the form of a
> SpatialPolygonsDataFrame. How do I get a numerical array of the x- and
> y-coordinates from my polygon that will go into the point.in.polygon
> function?
>
> Or for the over() function (x %over% y), with x as my SpatialPoints (the
> gps
> coordinates) and y as my SpatialPolygonsDataFrame (the basin), I receive
> the
> following error message, Error: identicalCRS(x, y) is not TRUE.
>
> Thanks for any suggestions.
>
>
>
> --
> View this message in context:
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>
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