convert the input sf to a different geometry
sf_cast(sf, to, close = TRUE, list_columns = NULL)object to convert
the geometry to convert to.
logical indicating if polygons should be closed
vector of column names or indexes. List columns are columns of data where there is a value corresponding to each coordinate in the geometry (sfc). List columns get cast with the geometries.
df <- data.frame(
id1 = c(1,1,1,1,1,1,1,1,2,2,2,2)
, id2 = c(1,1,1,1,2,2,2,2,1,1,1,1)
, x = c(0,0,1,1,1,1,2,2,3,4,4,3)
, y = c(0,1,1,0,1,2,2,1,3,3,4,4)
)
pt <- sf_point(obj = df, x = "x", y = "y", z = "id1")
mpt <- sf_multipoint(obj = df, x = "x", y = "y", multipoint_id = "id1")
ls <- sf_linestring(obj = df, x = "x", y = "y", linestring_id = "id1")
mls <- sf_multilinestring(obj = df, x = "x", y = "y", multilinestring_id = "id1")
p <- sf_polygon(
obj = df
, x = "x"
, y = "y"
, polygon_id = "id1"
, linestring_id = "id2"
, close = FALSE
)
mp <- sf_multipolygon(
obj = df
, x = "x"
, y = "y"
, multipolygon_id = "id1"
, linestring_id = "id2"
, close = FALSE
)
sf_cast( pt, "LINESTRING" )
#> geometry
#> 1 0, 0, 1
#> 2 0, 1, 1
#> 3 1, 1, 1
#> 4 1, 0, 1
#> 5 1, 1, 1
#> 6 1, 2, 1
#> 7 2, 2, 1
#> 8 2, 1, 1
#> 9 3, 3, 2
#> 10 4, 3, 2
#> 11 4, 4, 2
#> 12 3, 4, 2
sf_cast( mpt, "POLYGON" )
#> id1 geometry
#> 1 1 0, 0, 1, 1, 1, 1, 2, 2, 0, 0, 1, 1, 0, 1, 2, 2, 1, 0
#> 2 2 3, 4, 4, 3, 3, 3, 3, 4, 4, 3
sf_cast( ls, "POINT" )
#> id1 geometry
#> 1 1 0, 0
#> 2 1 0, 1
#> 3 1 1, 1
#> 4 1 1, 0
#> 5 1 1, 1
#> 6 1 1, 2
#> 7 1 2, 2
#> 8 1 2, 1
#> 9 2 3, 3
#> 10 2 4, 3
#> 11 2 4, 4
#> 12 2 3, 4
sf_cast( mls, "MULTIPOLYGON" )
#> id1 geometry
#> 1 1 0, 0, 1, 1, 1, 1, 2, 2, 0, 0, 1, 1, 0, 1, 2, 2, 1, 0
#> 2 2 3, 4, 4, 3, 3, 3, 3, 4, 4, 3
sf_cast( p, "POINT" )
#> id1 geometry
#> 1 1 0, 0
#> 2 1 0, 1
#> 3 1 1, 1
#> 4 1 1, 0
#> 5 1 1, 1
#> 6 1 1, 2
#> 7 1 2, 2
#> 8 1 2, 1
#> 9 2 3, 3
#> 10 2 4, 3
#> 11 2 4, 4
#> 12 2 3, 4
sf_cast( mp, "LINESTRING" )
#> id1 geometry
#> 1 1 0, 0, 1, 1, 0, 1, 1, 0
#> 2 1 1, 1, 2, 2, 1, 2, 2, 1
#> 3 2 3, 4, 4, 3, 3, 3, 4, 4
## List Columns
df <- data.frame(
id1 = c(1,1,1,1,1,1,1,1,2,2,2,2)
, id2 = c(1,1,1,1,2,2,2,2,1,1,1,1)
, x = c(0,0,1,1,1,1,2,2,3,4,4,3)
, y = c(0,1,1,0,1,2,2,1,3,3,4,4)
)
## Add a column where each value is an attribute of each coordinate
df$val <- letters[1:nrow(df)]
## Make a multipolygon, and specify `val` as a list_column
mp <- sf_multipolygon(
obj = df
, x = "x"
, y = "y"
, multipolygon_id = "id1"
, linestring_id = "id2"
, list_column = "val"
, keep = TRUE
, close = FALSE
)
## The 'val' attributes follow the same structure as the geometry column
## So each 'val' corresponds to a single coordinate in the geometry
str( mp )
#> Classes ‘sf’ and 'data.frame': 2 obs. of 3 variables:
#> $ id1 : num 1 2
#> $ val :List of 2
#> ..$ :List of 1
#> .. ..$ :List of 2
#> .. .. ..$ : chr "a" "b" "c" "d"
#> .. .. ..$ : chr "e" "f" "g" "h"
#> ..$ :List of 1
#> .. ..$ :List of 1
#> .. .. ..$ : chr "i" "j" "k" "l"
#> $ geometry:List of 2
#> ..$ :List of 1
#> .. ..$ :List of 2
#> .. .. ..$ : num [1:4, 1:2] 0 0 1 1 0 1 1 0
#> .. .. ..$ : num [1:4, 1:2] 1 1 2 2 1 2 2 1
#> .. ..- attr(*, "class")= chr [1:3] "XY" "MULTIPOLYGON" "sfg"
#> ..$ :List of 1
#> .. ..$ :List of 1
#> .. .. ..$ : num [1:4, 1:2] 3 4 4 3 3 3 4 4
#> .. ..- attr(*, "class")= chr [1:3] "XY" "MULTIPOLYGON" "sfg"
#> ..- attr(*, "n_empty")= int 0
#> ..- attr(*, "crs")=List of 2
#> .. ..$ input: chr NA
#> .. ..$ wkt : chr NA
#> .. ..- attr(*, "class")= chr "crs"
#> ..- attr(*, "class")= chr [1:2] "sfc_MULTIPOLYGON" "sfc"
#> ..- attr(*, "precision")= num 0
#> ..- attr(*, "bbox")= 'bbox' Named num [1:4] 0 0 4 4
#> .. ..- attr(*, "names")= chr [1:4] "xmin" "ymin" "xmax" "ymax"
#> - attr(*, "sf_column")= chr "geometry"
## specifying `list_columns = "val"` when casting will retain the association
## between the 'val' attribute and each coordinate.
res <- sf_cast( mp, "LINESTRING", list_columns = "val" )
## The 'val' attribute still follows the same structure as the geometry column
str( res )
#> Classes ‘sf’ and 'data.frame': 3 obs. of 3 variables:
#> $ id1 : num 1 1 2
#> $ val :List of 3
#> ..$ : chr "a" "b" "c" "d"
#> ..$ : chr "e" "f" "g" "h"
#> ..$ : chr "i" "j" "k" "l"
#> $ geometry:List of 3
#> ..$ : 'XY' num [1:4, 1:2] 0 0 1 1 0 1 1 0
#> ..$ : 'XY' num [1:4, 1:2] 1 1 2 2 1 2 2 1
#> ..$ : 'XY' num [1:4, 1:2] 3 4 4 3 3 3 4 4
#> ..- attr(*, "n_empty")= int 0
#> ..- attr(*, "crs")=List of 2
#> .. ..$ input: chr NA
#> .. ..$ wkt : chr NA
#> .. ..- attr(*, "class")= chr "crs"
#> ..- attr(*, "class")= chr [1:2] "sfc_LINESTRING" "sfc"
#> ..- attr(*, "precision")= num 0
#> ..- attr(*, "bbox")= 'bbox' Named num [1:4] 0 0 4 4
#> .. ..- attr(*, "names")= chr [1:4] "xmin" "ymin" "xmax" "ymax"
#> - attr(*, "sf_column")= chr "geometry"