tmap (version 4.0)

tm_shape: Shape (spatial object) specification

Description

Specify a shape, which is a spatial object from one of these spatial object class packages: sf, stars, or terra.

Usage

tm_shape(
  shp,
  bbox = NULL,
  crs = NULL,
  is.main = NA,
  name = NULL,
  unit = NULL,
  filter = NULL,
  ...
)

Arguments

shp

Spatial object

bbox

Bounding box of the map (only used if shp is the main shape (see is.main)

crs

Map projection (CRS). Can be set to an crs object (see sf::st_crs()), a proj4string, an EPSG number, the value "auto" (automatic crs recommendation), or one the the following generic projections: c("laea", "aeqd", "utm", "pconic", "eqdc", "stere"). See details.

is.main

Is shp the main shape, which determines the crs and bounding box of the map? By default, TRUE if it is the first tm_shape call

name

of the spatial object

unit

Unit of the coordinates

filter

Filter features

...

passed on to bb (e.g. ext can be used to enlarge or shrink a bounding box)

Details

The map projection (crs) determines in which coordinate system the spatial object is processed and plotted. See vignette about CRS. The crs can be specified in two places: 1) tm_shape() and tm_crs(). In both cases, the map is plotted into the specified crs. The difference is that in the first option, the crs is also taken into account in spatial transformation functions, such as the calculation of centroids and cartograms. In the second option, the crs is only used in the plotting phase.

The automatic crs recommendation (which is still work-in-progress) is the following:

Property	Recommendation
global (for world maps)	A pseudocylindrical projection tmap option crs_global, by default "eqearth (Equal Eearth). See https://r-tmap.github.io/tmap/articles/41_advanced_crs.html for more options
area (equal area)	Lambert Azimuthal Equal Area (laea)
distance (equidistant)	Azimuthal Equidistant (aeqd)
shape (conformal)	Stereographic (stere)

For further info about the available "generic" projects see: for utm: https://proj.org/en/9.4/operations/projections/utm.html for laea: https://proj.org/en/9.4/operations/projections/laea.html for aeqd: https://proj.org/en/9.4/operations/projections/aeqd.html for pconic: https://proj.org/en/9.4/operations/projections/pconic.html for eqdc: https://proj.org/en/9.4/operations/projections/eqdc.html

See Also

vignette about CRS

Examples

tm_shape(World, crs = "auto") +
	tm_polygons()

tm_shape(World, crs = 3035, bb = "Europe") +
	tm_polygons()

tm_shape(World, crs = "+proj=robin", filter = World$continent=="Africa") +
	tm_polygons()