R/geom-transformers.R
geos_unary.Rd
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_concave_hull(x, ratio, ..., allow_holes)
st_simplify(x, preserveTopology, dTolerance = 0)
st_triangulate(x, dTolerance = 0, bOnlyEdges = FALSE)
st_triangulate_constrained(x)
st_inscribed_circle(x, dTolerance, ...)
st_minimum_rotated_rectangle(x, ...)
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, ...)
object of class sfg
, sfc
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; if TRUE
, single-sided buffers are returned for linear geometries,
in which case negative dist
values give buffers on the right-hand side, positive on the left.
ignored
numeric; fraction convex: 1 returns the convex hulls, 0 maximally concave hulls
logical; if TRUE
, the resulting concave hull may have holes
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. If not specified (i.e. the default), then it is internally
set equal to FALSE
when the input data is specified with projected
coordinates or sf_use_s2()
returns FALSE
. Ignored in all the
other cases (with a warning when set equal to FALSE
) since the
function implicitly calls s2::s2_simplify
which always preserve
topological relationships (per single feature).
numeric; tolerance parameter, specified for all or for each
feature geometry. If you run st_simplify
, the input data is
specified with long-lat coordinates and sf_use_s2()
returns
TRUE
, then the value of dTolerance
must be specified in
meters.
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
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.
If a negative buffer returns empty polygons instead of shrinking, set st_use_s2() to FALSE
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_concave_hull
creates the concave hull of a geometry
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_triangulate_constrained
returns the constrained delaunay triangulation of polygons; requires GEOS version 3.10 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_minimum_rotated_rectangle
returns the minimum
rotated rectangular POLYGON which encloses the input geometry. The
rectangle has width equal to the minimum diameter, and a longer
length. If the convex hill of the input is degenerate (a line or
point) a linestring or point is returned.
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
chull for a more efficient algorithm for calculating the convex hull
## 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"))
#> Reading layer `nc' from data source
#> `/tmp/RtmpxmZ5jE/temp_libpathf41261b39098/sf/shape/nc.shp'
#> using driver `ESRI Shapefile'
#> Simple feature collection with 100 features and 14 fields
#> Geometry type: MULTIPOLYGON
#> Dimension: XY
#> Bounding box: xmin: -84.32385 ymin: 33.88199 xmax: -75.45698 ymax: 36.58965
#> Geodetic CRS: NAD27
nc_g = st_geometry(nc)
plot(st_convex_hull(nc_g))
plot(nc_g, border = grey(.5), add = TRUE)
set.seed(131)
if (compareVersion(sf_extSoftVersion()[["GEOS"]], "3.11.0") > -1) {
pts = cbind(runif(100), runif(100))
m = st_multipoint(pts)
co = sf:::st_concave_hull(m, 0.3)
coh = sf:::st_concave_hull(m, 0.3, allow_holes = TRUE)
plot(co, col = 'grey')
plot(coh, add = TRUE, border = 'red')
plot(m, add = TRUE)
}
# st_simplify examples:
op = par(mfrow = c(2, 3), mar = rep(0, 4))
plot(nc_g[1])
plot(st_simplify(nc_g[1], dTolerance = 1e3)) # 1000m
plot(st_simplify(nc_g[1], dTolerance = 5e3)) # 5000m
nc_g_planar = st_transform(nc_g, 2264) # planar coordinates, US foot
plot(nc_g_planar[1])
plot(st_simplify(nc_g_planar[1], dTolerance = 1e3)) # 1000 foot
plot(st_simplify(nc_g_planar[1], dTolerance = 5e3)) # 5000 foot
par(op)
if (compareVersion(sf_extSoftVersion()[["GEOS"]], "3.10.0") > -1) {
pts = rbind(c(0,0), c(1,0), c(1,1), c(.5,.5), c(0,1), c(0,0))
po = st_polygon(list(pts))
co = st_triangulate_constrained(po)
tr = st_triangulate(po)
plot(po, col = NA, border = 'grey', lwd = 15)
plot(tr, border = 'green', col = NA, lwd = 5, add = TRUE)
plot(co, border = 'red', col = 'NA', add = TRUE)
}
if (compareVersion(sf_extSoftVersion()[["GEOS"]], "3.9.0") > -1) {
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 (compareVersion(sf_extSoftVersion()[["GEOS"]], "3.5.0") > -1) {
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))
#> Geometry set for 1 feature
#> Geometry type: GEOMETRYCOLLECTION
#> Dimension: XY
#> Bounding box: xmin: 0 ymin: 0 xmax: 1 ymax: 1
#> CRS: NA
#> GEOMETRYCOLLECTION (POLYGON ((0 0, 0 1, 1 1, 0 ...
mls = st_multilinestring(list(rbind(c(0,0), c(1,1)), rbind(c(2,0), c(1,1))))
st_line_merge(st_sfc(mls))
#> Geometry set for 1 feature
#> Geometry type: LINESTRING
#> Dimension: XY
#> Bounding box: xmin: 0 ymin: 0 xmax: 2 ymax: 1
#> CRS: NA
#> LINESTRING (0 0, 1 1, 2 0)
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')
#> Warning: st_point_on_surface may not give correct results for longitude/latitude data
if (compareVersion(sf_extSoftVersion()[["GEOS"]], "3.7.0") > -1) {
st_reverse(st_linestring(rbind(c(1,1), c(2,2), c(3,3))))
}
#> LINESTRING (3 3, 2 2, 1 1)
(l = st_linestring(rbind(c(0,0), c(1,1), c(0,1), c(1,0), c(0,0))))
#> LINESTRING (0 0, 1 1, 0 1, 1 0, 0 0)
st_polygonize(st_node(l))
#> GEOMETRYCOLLECTION (POLYGON ((0 0, 0.5 0.5, 1 0, 0 0)), POLYGON ((0.5 0.5, 0 1, 1 1, 0.5 0.5)))
st_node(st_multilinestring(list(rbind(c(0,0), c(1,1), c(0,1), c(1,0), c(0,0)))))
#> MULTILINESTRING ((0 0, 0.5 0.5), (0.5 0.5, 1 1, 0 1, 0.5 0.5), (0.5 0.5, 1 0, 0 0))
sf = st_sf(a=1, geom=st_sfc(st_linestring(rbind(c(0,0),c(1,1)))), crs = 4326)
if (require(lwgeom, quietly = TRUE)) {
seg = st_segmentize(sf, units::set_units(100, km))
seg = st_segmentize(sf, units::set_units(0.01, rad))
nrow(seg$geom[[1]])
}
#> Linking to liblwgeom 3.0.0beta1 r16016, GEOS 3.10.2, PROJ 8.2.1
#> [1] 5