Define a geographic region

Creates a geographic region (a polygon) on a given map and gives it a name. This can be used to define objects which can be reused in multiple places in a slendr script (such as region arguments of population) without having to repeatedly define polygon coordinates.

Usage

region(name = NULL, map = NULL, center = NULL, radius = NULL, polygon = NULL)

Arguments

name

Name of the geographic region

map

Object of the type sf which defines the map

center

Two-dimensional vector specifying the center of the circular range

radius

Radius of the circular range

polygon

List of vector pairs, defining corners of the polygon range or a geographic region of the class slendr_region from which the polygon coordinates will be extracted (see the region() function)

Value

Object of the class slendr_region which encodes a standard spatial object of the class sf with several additional attributes (most importantly a corresponding slendr_map object, if applicable).

Examples

# create a blank abstract world 1000x1000 distance units in size
blank_map <- world(xrange = c(0, 1000), yrange = c(0, 1000), landscape = "blank")

# it is possible to construct custom landscapes (islands, corridors, etc.)
island1 <- region("island1", polygon = list(c(10, 30), c(50, 30), c(40, 50), c(0, 40)))
island2 <- region("island2", polygon = list(c(60, 60), c(80, 40), c(100, 60), c(80, 80)))
island3 <- region("island3", center = c(20, 80), radius = 10)
archipelago <- island1 %>% join(island2) %>% join(island3)

custom_map <- world(xrange = c(1, 100), c(1, 100), landscape = archipelago)

# real Earth landscapes can be defined using freely-available Natural Earth
# project data and with the possibility to specify an appropriate Coordinate
# Reference System, such as this example of a map of Europe

real_map <- world(xrange = c(-15, 40), yrange = c(30, 60), crs = "EPSG:3035")
#> Reading layer `ne_110m_land' from data source 
#>   `/private/var/folders/70/b_q2zdh116b9pfg29p03sx600000gn/T/RtmpyvLhIq/naturalearth/ne_110m_land.shp' 
#>   using driver `ESRI Shapefile'
#> Simple feature collection with 127 features and 3 fields
#> Geometry type: POLYGON
#> Dimension:     XY
#> Bounding box:  xmin: -180 ymin: -90 xmax: 180 ymax: 83.64513
#> Geodetic CRS:  WGS 84