Create sf object — sf-object • sf

Create sf, which extends data.frame-like objects with a simple feature list column

Usage

st_sf(
  ...,
  agr = NA_agr_,
  row.names,
  stringsAsFactors = sf_stringsAsFactors(),
  crs,
  precision,
  sf_column_name = NULL,
  check_ring_dir = FALSE,
  sfc_last = TRUE
)

# S3 method for sf
[(x, i, j, ..., drop = FALSE, op = st_intersects)

# S3 method for sf
print(x, ..., n = getOption("sf_max_print", default = 10))

Arguments

...: column elements to be binded into an sf object or a single list or data.frame with such columns; at least one of these columns shall be a geometry list-column of class sfc or be a list-column that can be converted into an sfc by st_as_sfc.
agr: character vector; see details below.
row.names: row.names for the created sf object
stringsAsFactors: logical; see st_read
crs: coordinate reference system, something suitable as input to st_crs
precision: numeric; see st_as_binary
sf_column_name: character; name of the active list-column with simple feature geometries; in case there is more than one and sf_column_name is NULL, the first one is taken.
check_ring_dir: see st_read
sfc_last: logical; if TRUE, sfc columns are always put last, otherwise column order is left unmodified.
x: object of class sf
i: record selection, see [.data.frame, or a sf object to work with the op argument
j: variable selection, see [.data.frame
drop: logical, default FALSE; if TRUE drop the geometry column and return a data.frame, else make the geometry sticky and return a sf object.
op: function; geometrical binary predicate function to apply when i is a simple feature object
n: maximum number of features to print; can be set globally by options(sf_max_print=...)

Details

agr, attribute-geometry-relationship, specifies for each non-geometry attribute column how it relates to the geometry, and can have one of following values: "constant", "aggregate", "identity". "constant" is used for attributes that are constant throughout the geometry (e.g. land use), "aggregate" where the attribute is an aggregate value over the geometry (e.g. population density or population count), "identity" when the attributes uniquely identifies the geometry of particular "thing", such as a building ID or a city name. The default value, NA_agr_, implies we don't know.

When a single value is provided to agr, it is cascaded across all input columns; otherwise, a named vector like c(feature1='constant', ...) will set agr value to 'constant' for the input column named feature1. See demo(nc) for a worked example of this.

When confronted with a data.frame-like object, st_sf will try to find a geometry column of class sfc, and otherwise try to convert list-columns when available into a geometry column, using st_as_sfc.

[.sf will return a data.frame or vector if the geometry column (of class sfc) is dropped (drop=TRUE), an sfc object if only the geometry column is selected, and otherwise return an sf object; see also [.data.frame; for [.sf ... arguments are passed to op.

Examples

g = st_sfc(st_point(1:2))
st_sf(a=3,g)
#> Simple feature collection with 1 feature and 1 field
#> Geometry type: POINT
#> Dimension:     XY
#> Bounding box:  xmin: 1 ymin: 2 xmax: 1 ymax: 2
#> CRS:           NA
#>   a           g
#> 1 3 POINT (1 2)
st_sf(g, a=3)
#> Simple feature collection with 1 feature and 1 field
#> Geometry type: POINT
#> Dimension:     XY
#> Bounding box:  xmin: 1 ymin: 2 xmax: 1 ymax: 2
#> CRS:           NA
#>   a           g
#> 1 3 POINT (1 2)
st_sf(a=3, st_sfc(st_point(1:2))) # better to name it!
#> Simple feature collection with 1 feature and 1 field
#> Geometry type: POINT
#> Dimension:     XY
#> Bounding box:  xmin: 1 ymin: 2 xmax: 1 ymax: 2
#> CRS:           NA
#>   a st_sfc.st_point.1.2..
#> 1 3           POINT (1 2)
# create empty structure with preallocated empty geometries:
nrows <- 10
geometry = st_sfc(lapply(1:nrows, function(x) st_geometrycollection()))
df <- st_sf(id = 1:nrows, geometry = geometry)
g = st_sfc(st_point(1:2), st_point(3:4))
s = st_sf(a=3:4, g)
s[1,]
#> Simple feature collection with 1 feature and 1 field
#> Geometry type: POINT
#> Dimension:     XY
#> Bounding box:  xmin: 1 ymin: 2 xmax: 1 ymax: 2
#> CRS:           NA
#>   a           g
#> 1 3 POINT (1 2)
class(s[1,])
#> [1] "sf"         "data.frame"
s[,1]
#> Simple feature collection with 2 features and 1 field
#> Geometry type: POINT
#> Dimension:     XY
#> Bounding box:  xmin: 1 ymin: 2 xmax: 3 ymax: 4
#> CRS:           NA
#>   a           g
#> 1 3 POINT (1 2)
#> 2 4 POINT (3 4)
class(s[,1])
#> [1] "sf"         "data.frame"
s[,2]
#> Simple feature collection with 2 features and 0 fields
#> Geometry type: POINT
#> Dimension:     XY
#> Bounding box:  xmin: 1 ymin: 2 xmax: 3 ymax: 4
#> CRS:           NA
#>             g
#> 1 POINT (1 2)
#> 2 POINT (3 4)
class(s[,2])
#> [1] "sf"         "data.frame"
g = st_sf(a=2:3, g)
pol = st_sfc(st_polygon(list(cbind(c(0,3,3,0,0),c(0,0,3,3,0)))))
h = st_sf(r = 5, pol)
g[h,]
#> Simple feature collection with 1 feature and 1 field
#> Geometry type: POINT
#> Dimension:     XY
#> Bounding box:  xmin: 1 ymin: 2 xmax: 1 ymax: 2
#> CRS:           NA
#>   a           g
#> 1 2 POINT (1 2)
h[g,]
#> Simple feature collection with 1 feature and 1 field
#> Geometry type: POLYGON
#> Dimension:     XY
#> Bounding box:  xmin: 0 ymin: 0 xmax: 3 ymax: 3
#> CRS:           NA
#>   r                            pol
#> 1 5 POLYGON ((0 0, 3 0, 3 3, 0 ...