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)st_boundary(x)
st_convex_hull(x)
st_simplify(x, preserveTopology = FALSE, dTolerance = 0)
st_triangulate(x, dTolerance = 0, bOnlyEdges = FALSE)
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_node(x)
st_segmentize(x, dfMaxLength, ...)
object of class sfg, sfg or sf
numeric; buffer distance for all, or for each of the elements in x; in case
dist is a units object, it should be convertible to arc_degree if
x has geographic coordinates, and to st_crs(x)$units otherwise
integer; number of segments per quadrant (fourth of a circle), for all or per-feature
character; style of line ends, one of 'ROUND', 'FLAT', 'SQUARE'
character; style of line joins, one of 'ROUND', 'MITRE', 'BEVEL'
numeric; limit of extension for a join if joinStyle 'MITRE' is used (default 1.0, minimum 0.0)
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.
numeric; tolerance parameter, specified for all or for each feature geometry.
logical; if TRUE, return lines, else return polygons
object of class sfc or sfg containing a POLYGON with the envelope for a voronoi diagram; this only takes effect when it is larger than the default envelope, chosen when envelope is an empty polygon
ignored
logical; for st_centroid: if TRUE, return centroid of the largest (sub)polygon of a MULTIPOLYGON rather than of the whole MULTIPOLYGON
maximum length of a line segment. If x has geographical coordinates (long/lat), dfMaxLength is either a numeric expressed in meter, or an object of class units with length units rad or degree; segmentation in the long/lat case takes place along the great circle, using st_geod_segmentize.
an object of the same class of x, with manipulated geometry.
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_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_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
# NOT RUN {
## 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"))
plot(st_convex_hull(nc))
plot(nc, border = grey(.5))
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)
}
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, axes = TRUE)
plot(st_centroid(nc), add = TRUE, pch = 3)
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, axes = TRUE)
plot(st_point_on_surface(nc), add = TRUE, pch = 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]])
# }
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