Largest polygon in a SpatialPolygons object
get_largest_polygon(sp, ...)Arguments
- sp
object with class
sp::SpatialPolygonsthat may contain one or more closed polygons.- ...
additional arguments are ignored.
Details
This function returns the largest polygon in a
sp::SpatialPolygons object, notably when there
are multiple polygons contained in one object.
The function calculates the largest area using
rgeos:gArea().
If two polygons have identical area, the first polygon is returned.
This function calls a helper function sp::disaggregate()
which creates one sp::SpatialPolygons object
for each individual polygon in the source object.
See also
Other venndir spatial:
degrees_to_adj(),
diff_degrees(),
display_angles(),
get_sp_buffer(),
intersect_polygons(),
mean_degree_arc(),
mean_degrees(),
nudge_sp(),
rescale_coordinates(),
rescale_sp(),
sp_circles(),
sp_ellipses(),
spread_degrees(),
union_polygons()
Examples
circles <- get_venn_shapes(c(A=1, B=2, "A&B"=3), proportional=TRUE)
col3 <- c("#FF000077", "#0000FF77")
sp::plot(circles)
circles_u12 <- union_polygons(circles[1:2]);
circles_i12 <- intersect_polygons(circles[1:2]);
# one SpatialPolygons object with multiple polygon pieces
circles_d12 <- rgeos::gDifference(circles_u12, circles_i12)
plot(circles_d12, add=TRUE, col="gold", lwd=3)
circles_d12_largest <- get_largest_polygon(circles_d12);
plot(circles_d12_largest, add=TRUE, border="red", lwd=5);
