GEOMETRY or GEOMETRYCOLLECTION,
return an object consisting only of elements of the specified type.R/collection_extract.R
st_collection_extract.RdSimilar to ST_CollectionExtract in PostGIS. If there are no sub-geometries of the specified type, an empty geometry is returned.
st_collection_extract( x, type = c("POLYGON", "POINT", "LINESTRING"), warn = FALSE ) # S3 method for sfg st_collection_extract( x, type = c("POLYGON", "POINT", "LINESTRING"), warn = FALSE ) # S3 method for sfc st_collection_extract( x, type = c("POLYGON", "POINT", "LINESTRING"), warn = FALSE ) # S3 method for sf st_collection_extract( x, type = c("POLYGON", "POINT", "LINESTRING"), warn = FALSE )
| x | an object of class |
|---|---|
| type | character; one of "POLYGON", "POINT", "LINESTRING" |
| warn | logical; if |
An object having the same class as x, with geometries
consisting only of elements of the specified type.
For sfg objects, an sfg object is returned if there is only
one geometry of the specified type, otherwise the geometries are combined
into an sfc object of the relevant type. If any subgeometries in the
input are MULTI, then all of the subgeometries in the output will be MULTI.
pt <- st_point(c(1, 0)) ls <- st_linestring(matrix(c(4, 3, 0, 0), ncol = 2)) poly1 <- st_polygon(list(matrix(c(5.5, 7, 7, 6, 5.5, 0, 0, -0.5, -0.5, 0), ncol = 2))) poly2 <- st_polygon(list(matrix(c(6.6, 8, 8, 7, 6.6, 1, 1, 1.5, 1.5, 1), ncol = 2))) multipoly <- st_multipolygon(list(poly1, poly2)) i <- st_geometrycollection(list(pt, ls, poly1, poly2)) j <- st_geometrycollection(list(pt, ls, poly1, poly2, multipoly)) st_collection_extract(i, "POLYGON")#> Geometry set for 2 features #> geometry type: POLYGON #> dimension: XY #> bbox: xmin: 5.5 ymin: -0.5 xmax: 8 ymax: 1.5 #> CRS: NA#>#>st_collection_extract(i, "POINT")#>st_collection_extract(i, "LINESTRING")#>## A GEOMETRYCOLLECTION aa <- rbind(st_sf(a=1, geom = st_sfc(i)), st_sf(a=2, geom = st_sfc(j))) ## With sf objects st_collection_extract(aa, "POLYGON")#> Simple feature collection with 5 features and 1 field #> geometry type: MULTIPOLYGON #> dimension: XY #> bbox: xmin: 5.5 ymin: -0.5 xmax: 8 ymax: 1.5 #> CRS: NA #> a geom #> 1.2 1 MULTIPOLYGON (((5.5 0, 7 0,... #> 1.3 1 MULTIPOLYGON (((6.6 1, 8 1,... #> 2.2 2 MULTIPOLYGON (((5.5 0, 7 0,... #> 2.3 2 MULTIPOLYGON (((6.6 1, 8 1,... #> 2.4 2 MULTIPOLYGON (((5.5 0, 7 0,...st_collection_extract(aa, "LINESTRING")#> Simple feature collection with 2 features and 1 field #> geometry type: LINESTRING #> dimension: XY #> bbox: xmin: 3 ymin: 0 xmax: 4 ymax: 0 #> CRS: NA #> a geom #> 1.1 1 LINESTRING (4 0, 3 0) #> 2.1 2 LINESTRING (4 0, 3 0)st_collection_extract(aa, "POINT")#> Simple feature collection with 2 features and 1 field #> geometry type: POINT #> dimension: XY #> bbox: xmin: 1 ymin: 0 xmax: 1 ymax: 0 #> CRS: NA #> a geom #> 1 1 POINT (1 0) #> 2 2 POINT (1 0)#> Geometry set for 5 features #> geometry type: MULTIPOLYGON #> dimension: XY #> bbox: xmin: 5.5 ymin: -0.5 xmax: 8 ymax: 1.5 #> CRS: NA#>#>#>#>#>#> Geometry set for 2 features #> geometry type: LINESTRING #> dimension: XY #> bbox: xmin: 3 ymin: 0 xmax: 4 ymax: 0 #> CRS: NA#>#>#> Geometry set for 2 features #> geometry type: POINT #> dimension: XY #> bbox: xmin: 1 ymin: 0 xmax: 1 ymax: 0 #> CRS: NA#>#>## A GEOMETRY of single types bb <- rbind( st_sf(a = 1, geom = st_sfc(pt)), st_sf(a = 2, geom = st_sfc(ls)), st_sf(a = 3, geom = st_sfc(poly1)), st_sf(a = 4, geom = st_sfc(multipoly)) ) st_collection_extract(bb, "POLYGON")#> Simple feature collection with 2 features and 1 field #> geometry type: MULTIPOLYGON #> dimension: XY #> bbox: xmin: 5.5 ymin: -0.5 xmax: 8 ymax: 1.5 #> CRS: NA #> a geom #> 3 3 MULTIPOLYGON (((5.5 0, 7 0,... #> 4 4 MULTIPOLYGON (((5.5 0, 7 0,...## A GEOMETRY of mixed single types and GEOMETRYCOLLECTIONS cc <- rbind(aa, bb) st_collection_extract(cc, "POLYGON")#> Simple feature collection with 7 features and 1 field #> geometry type: MULTIPOLYGON #> dimension: XY #> bbox: xmin: 5.5 ymin: -0.5 xmax: 8 ymax: 1.5 #> CRS: NA #> a geom #> 1.2 1 MULTIPOLYGON (((5.5 0, 7 0,... #> 1.3 1 MULTIPOLYGON (((6.6 1, 8 1,... #> 2.2 2 MULTIPOLYGON (((5.5 0, 7 0,... #> 2.3 2 MULTIPOLYGON (((6.6 1, 8 1,... #> 2.4 2 MULTIPOLYGON (((5.5 0, 7 0,... #> 5 3 MULTIPOLYGON (((5.5 0, 7 0,... #> 6 4 MULTIPOLYGON (((5.5 0, 7 0,...