Hi,

To get the centroids, you just have to type this:

ctds<-coordinates(polygons)

polygons being a SpatialPolygons(DataFrame) object
and
ctds being a SpatialPoints(DataFrame) object

2011/5/14 elaine kuo <elaine.kuo.tw@gmail.com>

> Dear list,
>
> I have multiple bird distribution maps in the form of ArcGIS shape files.
> The distribution maps are composed of grid polygons. (1 grid= 100 km*
> 100km)
>
> Now I want to obtain the centroids of each bird distribution maps.
> In the first step, I use "Feature to point"  to retrieve centroid of each
> grid within the polygons.
> Then, please kindly advise if any method in R is available to get the
> centroid of the grid centroid of each polygons.
> Thank you in advance.
>
> Elaine
>
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