[R-sig-Geo] Area of overlap between 2 polygons

[Rolf Turner]

On 10/09/11 08:31, Ryan Briscoe Runquist wrote:
> Dear All,
>
> I am new to spatial analysis in R, and I wanted to know if anyone could help
> me.  I am interested in finding the area of overlap between the ranges of 2
> species.  I have downloaded herbarium record data for a genus of plants that
> includes species names and the lat/long coordinates of the record.  I would
> like to be able to compute:
> the minimum convex polygon for each species (I have been able to do this
> with earth.poly{fossil}),
> the area of that polygon (also obtainable through earth.poly{fossil}),
> and the centroid coordinate of the polygon.
>
> I would then like to take these polygons and determine the pairwise area of
> overlap between all species combination and the distance between centroids.
> I have not been able to find a function that will help me do this.  Is there
> a function for this type of analysis and what class of data do I need to
> make this work.  Thank you in advance for any assistance.

The undocumented functions overlap.owin() and overlap.xypolygon()
in the "spatstat" package should do what you want.

     cheers,

         Rolf Turner