Clipping polygons in R

Question

I have two dataframes with geocodes. The first looks something like this:

spoints<- data.frame(x=c(1,2,3,4,5,6),y=c(6,5,4,3,2,1))

spoints maps a country.

My second data frame looks like this:

polyData<-data.frame(x=c(1,2,3,4,5,6,7,8,9,10),y=c(10,9,8,7,6,5,4,3,2,1),
col=c("a","b","c",etc.), id=c("a","b","c",etc.), average=c(44,33,66,55,etc))

This one contains coordinates to create voronoi clusters/polygons. but these are sketching polygons overlapping into the ocean. So, I want to avoid that and have them stop at the country boundaries.

But now, I am having difficulty using GPC library or the others.

Could someone please help me with this?

can you use the [rgeos](http://cran.r-project.org/web/packages/rgeos/rgeos.pdf) library? The `gIntersection` function is what you want. — Andy W, Jul 13 '15 at 12:05

score 1 · Accepted Answer · answered Jul 14 '15 at 12:01

Here is an example using the rgeos library I mentioned in the comment.

library(rgeos)
library(sp)

#making set of polygons for illustration
d1 <- readWKT("POLYGON((0 0, 1 0, 1 1, 0 1, 0 0))")
Tri <- c("POLYGON((0.3 0.6, 0.6 0.6, 0.5 1.3, 0.3 0.6))",
         "POLYGON((0.7 0.3, 1.3 0.3, 1.1 0.6, 0.7 0.3))")
d2 <- readWKT(text=paste0("GEOMETRYCOLLECTION(",paste0(Tri,collapse=","),")"),
      id=c("a","b"))

plot(d1,xlim=c(0, 1.4), ylim=c(0, 1.4))
plot(d2,col='red',add=TRUE)

#now taking the intersection
d3 <- gIntersection(d1,d2,byid=TRUE)
plot(d3,col='blue',add=TRUE)

enter image description here

Clipping polygons in R

1 Answers1