[R] Identify points that lie within polygon

[Rui Barradas]

Hello,

With your example run and click 10 black points inside the area.

ploc <- locator(n=10)
points(ploc$x, ploc$y, pch = 19, col = "green", cex = 1)

Hope this helps,

Rui Barradas

Em 06-08-2012 16:05, Ally escreveu:
> I have a complex 2D polygon with thousands of vertices, and I'd like to be
> able to identify points from a large set contained within the polygon, and
> was wondering if there might be an efficient way of doing this?  Any advice
> would be useful!  Here is a small example of what I mean:
>
> # make polygon
> v1<-c(0,1,1,2,1,3,6,7)
> v2<-c(1,3,3,5,6,7,8,9)
> plot(v1, v2, type = "n" )
> polygon(v1, v2, lwd = 2, col = "red")
>
> # plot a set of candidate grid points
> grid<-seq(0, 10, length.out = 30)
> pts<-expand.grid(grid, grid)
> points(pts, pch = 19, col = 1, cex = 1)
>
> Many thanks!
>
> Alastair
>
>
>
>
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