Conversion to other formats: WKT, WKB, sp
Conversion to and from well-known text
The usual form in which we see simple features printed is well-known text:
st_point(c(0,1))
## POINT (0 1)
st_linestring(matrix(0:9,ncol=2,byrow=TRUE))
## LINESTRING (0 1, 2 3, 4 5, 6 7, 8 9)We can create these well-known text strings explicitly using
st_as_text:
x = st_linestring(matrix(0:9,ncol=2,byrow=TRUE))
str = st_as_text(x)
x
## LINESTRING (0 1, 2 3, 4 5, 6 7, 8 9)We can convert back from WKT by using st_as_sfc:
st_as_sfc(str)
## Geometry set for 1 feature
## Geometry type: LINESTRING
## Dimension: XY
## Bounding box: xmin: 0 ymin: 1 xmax: 8 ymax: 9
## CRS: NA
## LINESTRING (0 1, 2 3, 4 5, 6 7, 8 9)Conversion to and from well-known binary
Well-known binary is created from simple features by
st_as_binary:
x = st_linestring(matrix(0:9,ncol=2,byrow=TRUE))
(x = st_as_binary(x))
## [1] 01 02 00 00 00 05 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 f0 3f
## [26] 00 00 00 00 00 00 00 40 00 00 00 00 00 00 08 40 00 00 00 00 00 00 10 40 00
## [51] 00 00 00 00 00 14 40 00 00 00 00 00 00 18 40 00 00 00 00 00 00 1c 40 00 00
## [76] 00 00 00 00 20 40 00 00 00 00 00 00 22 40
class(x)
## [1] "raw"The object returned by st_as_binary is of class
WKB and is either a list with raw vectors, or a single raw
vector. These can be converted into a hexadecimal character vector using
rawToHex:
rawToHex(x)
## [1] "0102000000050000000000000000000000000000000000f03f000000000000004000000000000008400000000000001040000000000000144000000000000018400000000000001c4000000000000020400000000000002240"Converting back to sf uses st_as_sfc:
x = st_as_binary(st_sfc(st_point(0:1), st_point(5:6)))
st_as_sfc(x)
## Geometry set for 2 features
## Geometry type: POINT
## Dimension: XY
## Bounding box: xmin: 0 ymin: 1 xmax: 5 ymax: 6
## CRS: NA
## POINT (0 1)
## POINT (5 6)Conversion to and from sp
Spatial objects as maintained by package sp can be
converted into simple feature objects or geometries by
st_as_sf and st_as_sfc, respectively:
methods(st_as_sf)
## [1] st_as_sf.SpatVector* st_as_sf.Spatial* st_as_sf.data.frame*
## [4] st_as_sf.lpp* st_as_sf.map* st_as_sf.owin*
## [7] st_as_sf.ppp* st_as_sf.ppplist* st_as_sf.psp*
## [10] st_as_sf.s2_geography* st_as_sf.sf* st_as_sf.sfc*
## [13] st_as_sf.wk_crc* st_as_sf.wk_rct* st_as_sf.wk_wkb*
## [16] st_as_sf.wk_wkt* st_as_sf.wk_xy*
## see '?methods' for accessing help and source code
methods(st_as_sfc)
## [1] st_as_sfc.SpatialLines* st_as_sfc.SpatialMultiPoints*
## [3] st_as_sfc.SpatialPixels* st_as_sfc.SpatialPoints*
## [5] st_as_sfc.SpatialPolygons* st_as_sfc.WKB*
## [7] st_as_sfc.bbox* st_as_sfc.blob*
## [9] st_as_sfc.character* st_as_sfc.dimensions*
## [11] st_as_sfc.factor* st_as_sfc.list*
## [13] st_as_sfc.map* st_as_sfc.owin*
## [15] st_as_sfc.pq_geometry* st_as_sfc.psp*
## [17] st_as_sfc.raw* st_as_sfc.s2_geography*
## [19] st_as_sfc.sf* st_as_sfc.tess*
## [21] st_as_sfc.wk_crc* st_as_sfc.wk_rct*
## [23] st_as_sfc.wk_wkb* st_as_sfc.wk_wkt*
## [25] st_as_sfc.wk_xy*
## see '?methods' for accessing help and source codeAn example would be:
library(sp)
data(meuse)
coordinates(meuse) = ~x+y
m.sf = st_as_sf(meuse)
opar = par(mar=rep(0,4))
plot(m.sf)
## Warning: plotting the first 10 out of 12 attributes; use max.plot = 12 to plot
## all
Conversion of simple feature objects of class sf or
sfc into corresponding Spatial* objects is
done using the as method, coercing to
Spatial:
x = st_sfc(st_point(c(5,5)), st_point(c(6,9)), crs = 4326)
as(x, "Spatial")
## SpatialPoints:
## coords.x1 coords.x2
## [1,] 5 5
## [2,] 6 9
## Coordinate Reference System (CRS) arguments: +proj=longlat +datum=WGS84
## +no_defs