Geometric unary operations on simple feature geometry sets
Geometric unary operations on simple feature geometries. These are all generics, with methods for sfg, sfc and sf objects, returning an object of the same class. All operations work on a per-feature basis, ignoring all other features.
st_buffer( x, dist, nQuadSegs = 30, endCapStyle = "ROUND", joinStyle = "ROUND", mitreLimit = 1, singleSide = FALSE, ... ) st_boundary(x) st_convex_hull(x) st_simplify(x, preserveTopology = FALSE, dTolerance = 0) st_triangulate(x, dTolerance = 0, bOnlyEdges = FALSE) st_inscribed_circle(x, dTolerance, ...) st_voronoi(x, envelope, dTolerance = 0, bOnlyEdges = FALSE) st_polygonize(x) st_line_merge(x) st_centroid(x, ..., of_largest_polygon = FALSE) st_point_on_surface(x) st_reverse(x) st_node(x) st_segmentize(x, dfMaxLength, ...)
x |
object of class |
dist |
numeric; buffer distance for all, or for each of the elements in |
nQuadSegs |
integer; number of segments per quadrant (fourth of a circle), for all or per-feature |
endCapStyle |
character; style of line ends, one of 'ROUND', 'FLAT', 'SQUARE' |
joinStyle |
character; style of line joins, one of 'ROUND', 'MITRE', 'BEVEL' |
mitreLimit |
numeric; limit of extension for a join if |
singleSide |
logical; if |
... |
ignored |
preserveTopology |
logical; carry out topology preserving simplification? May be specified for each, or for all feature geometries. Note that topology is preserved only for single feature geometries, not for sets of them. |
dTolerance |
numeric; tolerance parameter, specified for all or for each feature geometry. |
bOnlyEdges |
logical; if TRUE, return lines, else return polygons |
envelope |
object of class |
of_largest_polygon |
logical; for |
dfMaxLength |
maximum length of a line segment. If |
st_buffer computes a buffer around this geometry/each geometry. If any of endCapStyle,
joinStyle, or mitreLimit are set to non-default values ('ROUND', 'ROUND', 1.0 respectively) then
the underlying 'buffer with style' GEOS function is used.
See postgis.net/docs/ST_Buffer.html for details.
st_boundary returns the boundary of a geometry
st_convex_hull creates the convex hull of a set of points
st_simplify simplifies lines by removing vertices
st_triangulate triangulates set of points (not constrained). st_triangulate requires GEOS version 3.4 or above
st_inscribed_circle returns the maximum inscribed circle for polygon geometries.
For st_inscribed_circle, if nQuadSegs is 0 a 2-point LINESTRING is returned with the
center point and a boundary point of every circle, otherwise a circle (buffer) is returned where
nQuadSegs controls the number of points per quadrant to approximate the circle.
st_inscribed_circle requires GEOS version 3.9 or above
st_voronoi creates voronoi tesselation. st_voronoi requires GEOS version 3.5 or above
st_polygonize creates polygon from lines that form a closed ring. In case of st_polygonize, x must be an object of class LINESTRING or MULTILINESTRING, or an sfc geometry list-column object containing these
st_line_merge merges lines. In case of st_line_merge, x must be an object of class MULTILINESTRING, or an sfc geometry list-column object containing these
st_centroid gives the centroid of a geometry
st_point_on_surface returns a point guaranteed to be on the (multi)surface.
st_reverse reverses the nodes in a line
st_node adds nodes to linear geometries at intersections without a node, and only works on individual linear geometries
st_segmentize adds points to straight lines
an object of the same class of x, with manipulated geometry.
## st_buffer, style options (taken from rgeos gBuffer)
l1 = st_as_sfc("LINESTRING(0 0,1 5,4 5,5 2,8 2,9 4,4 6.5)")
op = par(mfrow=c(2,3))
plot(st_buffer(l1, dist = 1, endCapStyle="ROUND"), reset = FALSE, main = "endCapStyle: ROUND")
plot(l1,col='blue',add=TRUE)
plot(st_buffer(l1, dist = 1, endCapStyle="FLAT"), reset = FALSE, main = "endCapStyle: FLAT")
plot(l1,col='blue',add=TRUE)
plot(st_buffer(l1, dist = 1, endCapStyle="SQUARE"), reset = FALSE, main = "endCapStyle: SQUARE")
plot(l1,col='blue',add=TRUE)
plot(st_buffer(l1, dist = 1, nQuadSegs=1), reset = FALSE, main = "nQuadSegs: 1")
plot(l1,col='blue',add=TRUE)
plot(st_buffer(l1, dist = 1, nQuadSegs=2), reset = FALSE, main = "nQuadSegs: 2")
plot(l1,col='blue',add=TRUE)
plot(st_buffer(l1, dist = 1, nQuadSegs= 5), reset = FALSE, main = "nQuadSegs: 5")
plot(l1,col='blue',add=TRUE)
par(op)
l2 = st_as_sfc("LINESTRING(0 0,1 5,3 2)")
op = par(mfrow = c(2, 3))
plot(st_buffer(l2, dist = 1, joinStyle="ROUND"), reset = FALSE, main = "joinStyle: ROUND")
plot(l2, col = 'blue', add = TRUE)
plot(st_buffer(l2, dist = 1, joinStyle="MITRE"), reset = FALSE, main = "joinStyle: MITRE")
plot(l2, col= 'blue', add = TRUE)
plot(st_buffer(l2, dist = 1, joinStyle="BEVEL"), reset = FALSE, main = "joinStyle: BEVEL")
plot(l2, col= 'blue', add=TRUE)
plot(st_buffer(l2, dist = 1, joinStyle="MITRE" , mitreLimit=0.5), reset = FALSE,
main = "mitreLimit: 0.5")
plot(l2, col = 'blue', add = TRUE)
plot(st_buffer(l2, dist = 1, joinStyle="MITRE",mitreLimit=1), reset = FALSE,
main = "mitreLimit: 1")
plot(l2, col = 'blue', add = TRUE)
plot(st_buffer(l2, dist = 1, joinStyle="MITRE",mitreLimit=3), reset = FALSE,
main = "mitreLimit: 3")
plot(l2, col = 'blue', add = TRUE)
par(op)
nc = st_read(system.file("shape/nc.shp", package="sf"))
nc_g = st_geometry(nc)
plot(st_convex_hull(nc_g))
plot(nc_g, border = grey(.5), add = TRUE)
if (sf_extSoftVersion()["GEOS"] >= "3.9.0") {
nc_t = st_transform(nc, 'EPSG:2264')
x = st_inscribed_circle(st_geometry(nc_t))
plot(st_geometry(nc_t), asp = 1, col = grey(.9))
plot(x, add = TRUE, col = '#ff9999')
}
set.seed(1)
x = st_multipoint(matrix(runif(10),,2))
box = st_polygon(list(rbind(c(0,0),c(1,0),c(1,1),c(0,1),c(0,0))))
if (sf_extSoftVersion()["GEOS"] >= "3.5.0") {
v = st_sfc(st_voronoi(x, st_sfc(box)))
plot(v, col = 0, border = 1, axes = TRUE)
plot(box, add = TRUE, col = 0, border = 1) # a larger box is returned, as documented
plot(x, add = TRUE, col = 'red', cex=2, pch=16)
plot(st_intersection(st_cast(v), box)) # clip to smaller box
plot(x, add = TRUE, col = 'red', cex=2, pch=16)
# matching Voronoi polygons to data points:
# https://github.com/r-spatial/sf/issues/1030
# generate 50 random unif points:
n = 100
pts = st_as_sf(data.frame(matrix(runif(n), , 2), id = 1:(n/2)), coords = c("X1", "X2"))
# compute Voronoi polygons:
pols = st_collection_extract(st_voronoi(do.call(c, st_geometry(pts))))
# match them to points:
pts$pols = pols[unlist(st_intersects(pts, pols))]
plot(pts["id"], pch = 16) # ID is color
plot(st_set_geometry(pts, "pols")["id"], xlim = c(0,1), ylim = c(0,1), reset = FALSE)
plot(st_geometry(pts), add = TRUE)
layout(matrix(1)) # reset plot layout
}
mls = st_multilinestring(list(matrix(c(0,0,0,1,1,1,0,0),,2,byrow=TRUE)))
st_polygonize(st_sfc(mls))
mls = st_multilinestring(list(rbind(c(0,0), c(1,1)), rbind(c(2,0), c(1,1))))
st_line_merge(st_sfc(mls))
plot(nc_g, axes = TRUE)
plot(st_centroid(nc_g), add = TRUE, pch = 3, col = 'red')
mp = st_combine(st_buffer(st_sfc(lapply(1:3, function(x) st_point(c(x,x)))), 0.2 * 1:3))
plot(mp)
plot(st_centroid(mp), add = TRUE, col = 'red') # centroid of combined geometry
plot(st_centroid(mp, of_largest_polygon = TRUE), add = TRUE, col = 'blue', pch = 3)
plot(nc_g, axes = TRUE)
plot(st_point_on_surface(nc_g), add = TRUE, pch = 3, col = 'red')
if (sf_extSoftVersion()["GEOS"] >= "3.7.0") {
st_reverse(st_linestring(rbind(c(1,1), c(2,2), c(3,3))))
}
(l = st_linestring(rbind(c(0,0), c(1,1), c(0,1), c(1,0), c(0,0))))
st_polygonize(st_node(l))
st_node(st_multilinestring(list(rbind(c(0,0), c(1,1), c(0,1), c(1,0), c(0,0)))))
sf = st_sf(a=1, geom=st_sfc(st_linestring(rbind(c(0,0),c(1,1)))), crs = 4326)
seg = st_segmentize(sf, units::set_units(100, km))
seg = st_segmentize(sf, units::set_units(0.01, rad))
nrow(seg$geom[[1]])Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.