[R] Points inside a polygon

[Rolf Turner]

On 12/01/12 17:28, Hasan Diwan wrote:
> I have a list of bounds for a series of polygons. I do understand the
> formula to determine whether point i is within polygon X (X[x1]<  i[x]
> &  X[x2]>  i[x]&  X[y1]<  i[y]&  X[y2]>  i[y]), and I can apply this
> throughout the dataset. However, this naive algorithm doesn't scale
> very well. The data set contains 10,000 points consisting of (n,e)
> pairs where I'm interested in which are inside polygons denoted by
> vertices (V[x1]/V[y1],V[x2],V[y2]). Is there a shortcut to accomplish
> this goal? Many thanks!  --

You could use the function inside.owin() in the "spatstat" package
(after appropriately reconfiguring your polygons as objects of class
"owin"; something like w <- owin(poly=plygn) where "plygn" is your
polygon).

You could also use the undocumented function inside.xypolygon().

     cheers,

         Rolf Turner