Unions and intersections (of artificial geometric objects)

The following makes use of the sf package. You may need to install it from CRAN using the code install.packages("sf") if you want to run this on your computer. (The package is already installed on the notebook container, however.)

library(sf)

Linking to GEOS 3.9.0, GDAL 3.2.2, PROJ 7.2.1; sf_use_s2() is TRUE

A <- rbind(
    c(0,0),
    c(2,0),
    c(0,2),
    c(0,0)
)
A <- st_polygon(list(A))
B <- rbind(
    c( 1, 1),
    c( 1,-1),
    c(-1,-1),
    c(-1, 1),
    c( 1, 1)
)
B <- st_polygon(list(B))

A

POLYGON ((0 0, 2 0, 0 2, 0 0))



B

POLYGON ((1 1, 1 -1, -1 -1, -1 1, 1 1))



plot(A,xlim=c(-1,2),ylim=c(-1,2))
plot(B,lty=2,add=TRUE)
text(0,1.5,"A",pos=2)
text(1,-.5,"B",pos=4)
text(.5,-1.5,"Two shapes A and B",pos=1)
/book/data-management-r/08-spatial-geographical-data/artificial-unions-intersections/7be70694e58f936d3a6f9a4fac81538fe7fdd7ee880e31360f084add4a82a1a7.png 
plot(st_union(A,B),col="gray70",xlim=c(-1,2),ylim=c(-1,2))
plot(A,lty=3,add=TRUE)
plot(B,lty=3,add=TRUE)
text(.5,-1.5,"st_union(A,B)",pos=1)
/book/data-management-r/08-spatial-geographical-data/artificial-unions-intersections/05834cbb35a78088adaf2a0f8f5d25465833b7f948b83fee5fdf2dc96202848c.png 
plot(A,lty=3,xlim=c(-1,2),ylim=c(-1,2))
plot(B,lty=3,add=TRUE)
plot(st_intersection(A,B),add=TRUE,col="gray70")
text(.5,-1.5,"st_intersection(A,B)",pos=1)
/book/data-management-r/08-spatial-geographical-data/artificial-unions-intersections/398e3c350f8ac5d8da71bc358d0a0f791816660b770198c6e0ebbb27e6cf4c14.png 
plot(st_difference(A,B),col="gray70",,xlim=c(-1,2),ylim=c(-1,2))
plot(A,lty=3,add=TRUE)
plot(B,lty=3,add=TRUE)
text(.5,-1.5,"st_difference(A,B)",pos=1)
/book/data-management-r/08-spatial-geographical-data/artificial-unions-intersections/e58ad834685da82ed8cd3d64b2aa86d076565ab9bd53b090ed96f0eae5f9201b.png 
plot(st_difference(B,A),col="gray70",,xlim=c(-1,2),ylim=c(-1,2))
plot(A,lty=3,add=TRUE)
plot(B,lty=3,add=TRUE)
text(.5,-1.5,"st_difference(B,A)",pos=1)
/book/data-management-r/08-spatial-geographical-data/artificial-unions-intersections/1a0bf66edec27e10494682add52759a39c45e7dc56ca25cfe169fcc5b348101c.png 
plot(st_sym_difference(A,B),col="gray70",,xlim=c(-1,2),ylim=c(-1,2))
text(.5,-1.5,"st_sym_difference(A,B)",pos=1)
/book/data-management-r/08-spatial-geographical-data/artificial-unions-intersections/7630f15b907730eca7ff5f7a8cff38bc9f4b0b67d4c2e676427bf3eb8fe49e44.png