Create sf object
Create sf, which extends data.frame-like objects with a simple feature list column
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 class 'sf'
x[i, j, ..., drop = FALSE, op = st_intersects]
## S3 method for class 'sf'
print(x, ..., n = getOption("sf_max_print", default = 10))... |
column elements to be binded into an |
agr |
character vector; see details below. |
row.names |
row.names for the created |
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 |
check_ring_dir |
see st_read |
sfc_last |
logical; if |
x |
object of class |
i |
record selection, see [.data.frame |
j |
variable selection, see [.data.frame |
drop |
logical, default |
op |
function; geometrical binary predicate function to apply when |
n |
maximum number of features to print; can be set globally by |
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.
g = st_sfc(st_point(1:2)) st_sf(a=3,g) st_sf(g, a=3) st_sf(a=3, st_sfc(st_point(1:2))) # better to name it! # 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,] class(s[1,]) s[,1] class(s[,1]) s[,2] class(s[,2]) 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,] h[g,]
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