Summarise changing geometries based on a group identifier

Changing geometries are summarised for all time periods as a single geometry (of types POINT, POLYGON, MULTIPOLYGON) in order to pass them as a spatial dimension to post_* objects. The family of functions summarise_geometry_*() or summarize_geometry_*() are helpers to create these summarised geometries.

Usage

summarise_geometry_union(
  x,
  group_id = NULL,
  sf_column_name = NULL,
  .checks = TRUE
)

summarize_geometry_union(
  x,
  group_id = NULL,
  sf_column_name = NULL,
  .checks = TRUE
)

summarise_geometry_centroid(
  x,
  group_id = NULL,
  sf_column_name = NULL,
  .checks = TRUE
)

summarize_geometry_centroid(
  x,
  group_id = NULL,
  sf_column_name = NULL,
  .checks = TRUE
)

summarise_geometry_bbox(
  x,
  group_id = NULL,
  sf_column_name = NULL,
  .checks = TRUE,
  rotated = FALSE
)

summarize_geometry_bbox(
  x,
  group_id = NULL,
  sf_column_name = NULL,
  .checks = TRUE,
  rotated = FALSE
)

summarise_geometry_convex_hull(
  x,
  group_id = NULL,
  sf_column_name = NULL,
  .checks = TRUE
)

summarize_geometry_convex_hull(
  x,
  group_id = NULL,
  sf_column_name = NULL,
  .checks = TRUE
)

Arguments

x: object POLYGON/MULTIPOLYGON changing geometries to summarise based on group_id.
group_id: see ?post_array for details. Defaults to the first non-spatial, non-temporal column in x.
sf_column_name: (character) name of column with changing geometries. Defaults to active sf_column.
.checks: internal, should creation arguments be checked?
rotated: (logical) if TRUE, the minimum rotated rectangle is returned, if FALSE the minimum unrotated rectangle or bounding box is returned. Defaults to FALSE

Value

object of class sfc with summarised geometries based on group_id

Details

A custom function to summarise geometries can be passed onto the coercion functions as_post_*(), given that the parameters x, group_id and sf_column_name are included in the function. Additional arguments can be passed to the function as necessary. See vignette("post02_geomsum") for more information.

Functions

summarise_geometry_union(): computes the geometry summary as the union and dissolve of the changing geometries
summarise_geometry_centroid(): computes the geometry summary as the centroid of the union and dissolve of the changing geometries
summarise_geometry_bbox(): computes the geometry summary as the bounding box or minimum rectangle of the union and dissolve of the changing geometries
summarise_geometry_convex_hull(): computes the geometry summary as the convex hull of the union and dissolve of the changing geometries

Examples

# union and dissolve
summarise_geometry_union(polygons)
#> Geometry set for 5 features 
#> Geometry type: POLYGON
#> Dimension:     XY
#> Bounding box:  xmin: -0.2974337 ymin: -0.0029756 xmax: 0.9730806 ymax: 1.153558
#> Geodetic CRS:  WGS 84
#> POLYGON ((0.4971355 0.8717961, 0.5474949 0.8088...
#> POLYGON ((-0.1774445 0.5995572, -0.1843257 0.58...
#> POLYGON ((0.28657 0.6085207, 0.2663408 0.622264...
#> POLYGON ((0.5737123 0.4613799, 0.6063966 0.4263...
#> POLYGON ((0.2973931 0.2557416, 0.2813385 0.2544...
# centroid
summarise_geometry_centroid(polygons)
#> Geometry set for 5 features 
#> Geometry type: POINT
#> Dimension:     XY
#> Bounding box:  xmin: -0.002543201 ymin: 0.17772 xmax: 0.752585 ymax: 0.9018588
#> Geodetic CRS:  WGS 84
#> POINT (0.647816 0.9018588)
#> POINT (-0.002543201 0.8403816)
#> POINT (0.3897167 0.5412363)
#> POINT (0.752585 0.3538271)
#> POINT (0.4690683 0.17772)
# bounding box or minimum unrotated rectangle
summarise_geometry_bbox(polygons)
#> Geometry set for 5 features 
#> Geometry type: POLYGON
#> Dimension:     XY
#> Bounding box:  xmin: -0.2974337 ymin: -0.0029756 xmax: 0.9730806 ymax: 1.153558
#> Geodetic CRS:  WGS 84
#> POLYGON ((0.4361026 0.7456421, 0.9005707 0.7456...
#> POLYGON ((-0.2974337 0.5814869, 0.3796448 0.581...
#> POLYGON ((0.2145846 0.4039274, 0.5898739 0.4039...
#> POLYGON ((0.5272362 0.1748722, 0.9730806 0.1748...
#> POLYGON ((0.2452129 -0.0029756, 0.6988282 -0.00...
# minimum rotated rectangle
summarise_geometry_bbox(polygons, rotated = TRUE)
#> Warning: st_minimum_rotated_rectangle does not work correctly for longitude/latitude data
#> Geometry set for 5 features 
#> Geometry type: POLYGON
#> Dimension:     XY
#> Bounding box:  xmin: -0.4068963 ymin: -0.05907163 xmax: 0.9881167 ymax: 1.232265
#> Geodetic CRS:  WGS 84
#> POLYGON ((0.5137787 1.117004, 0.3759687 0.90381...
#> POLYGON ((0.3796448 0.767853, 0.2316513 1.23226...
#> POLYGON ((0.3321186 0.7217665, 0.1760477 0.4920...
#> POLYGON ((0.6633874 0.573032, 0.500051 0.369666...
#> POLYGON ((0.678186 -0.05907163, 0.7911437 0.289...
# convex hull
summarise_geometry_convex_hull(polygons)
#> Geometry set for 5 features 
#> Geometry type: POLYGON
#> Dimension:     XY
#> Bounding box:  xmin: -0.2974337 ymin: -0.0029756 xmax: 0.9730806 ymax: 1.153558
#> Geodetic CRS:  WGS 84
#> POLYGON ((0.7568336 0.7456421, 0.8157179 0.7671...
#> POLYGON ((-0.2341393 0.5814869, -0.1843257 0.58...
#> POLYGON ((0.4606164 0.4039274, 0.5749458 0.4441...
#> POLYGON ((0.8757658 0.1748722, 0.8918794 0.1923...
#> POLYGON ((0.505091 -0.0029756, 0.6988282 0.0046...