Filter and cast geometries

This function filters a given geometries by specific type and casts it to the specified type.

Usage

filter_and_cast_geometries(
  geometries,
  geometry_type = c("POINT", "LINESTRING", "POLYGON")
)

get_points(geometries)

get_linestrings(geometries)

get_polygons(geometries)

Arguments

geometries

A sf object representing geometries.

geometry_type

The type of geometry to filter and cast to. Must be one of "POINT", "LINESTRING", or "POLYGON".

Value

A sf object containing only the specified type of geometry.

Examples

plot(1, type = "n", xlab = "", ylab = "", axes = FALSE, xlim = c(0, 12), ylim = c(0, 10))
text(0, c(2, 6), c("Single", "Multiple"), srt = 90, cex = 1)
text(c(2, 6, 10), 8, c("Point", "Linestring", "Polygon"), cex = 1)

geometries <- sf::st_sf(geometry = c(
  # POINT
  create_points(2, 2),
  # LINESTRING
  create_linestring(5, 1, 7, 3),
  # POLYGON
  create_polygon(9, 1, 9, 3, 11, 3, 11, 1),
  # MULTIPOINT
  sf::st_union(create_points(1, 7, 2, 6, 3, 5)),
  # MULTILINESTRING
  sf::st_union(
    create_linestring(5, 6, 6, 7),
    create_linestring(6, 5, 7, 6)
  ),
  # MULTIPOLYGON
  sf::st_union(
    create_polygon(9, 7, 10, 7, 10, 6, 9, 6),
    create_polygon(10, 5, 11, 6, 11, 5)
  )
))
plot(geometries, pch = 16, lwd = 2, add = TRUE)


# Get points from geometries
plot(get_points(geometries), pch = 16)


# Get linestrings from geometries
plot(get_linestrings(geometries), lwd = 2)


# Get polygons from geometries
plot(get_polygons(geometries), lwd = 2)