map_coloring: Map coloring
In tmaptools: Thematic Map Tools

Description Usage Arguments Value Examples

Color the polygons of a map such that adjacent polygons have different colors

map_coloring(
  x,
  algorithm = "greedy",
  ncols = NA,
  minimize = FALSE,
  palette = NULL,
  contrast = 1
)

`x`	Either a shape (i.e. a `sf` or `SpatialPolygons(DataFrame)` (`sp` package) object), or an adjacency list.
`algorithm`	currently, only "greedy" is implemented.
`ncols`	number of colors. By default it is 8 when `palette` is undefined. Else, it is set to the length of `palette`
`minimize`	logical that determines whether `algorithm` will search for a minimal number of colors. If `FALSE`, the `ncols` colors will be picked by a random procedure.
`palette`	color palette.
`contrast`	vector of two numbers that determine the range that is used for sequential and diverging palettes (applicable when `auto.palette.mapping=TRUE`). Both numbers should be between 0 and 1. The first number determines where the palette begins, and the second number where it ends. For sequential palettes, 0 means the brightest color, and 1 the darkest color. For diverging palettes, 0 means the middle color, and 1 both extremes. If only one number is provided, this number is interpreted as the endpoint (with 0 taken as the start).

If palette is defined, a vector of colors is returned, otherwise a vector of color indices.

if (require(tmap) && packageVersion("tmap") >= "2.0") {
    data(World, metro)

    World$color <- map_coloring(World, palette="Pastel2")
    qtm(World, fill = "color")

    # map_coloring used indirectly: qtm(World, fill = "MAP_COLORS")

    data(NLD_prov, NLD_muni)
    tm_shape(NLD_prov) +
    	tm_fill("name", legend.show = FALSE) +
    tm_shape(NLD_muni) +
    	tm_polygons("MAP_COLORS", palette="Greys", alpha = .25) +
    tm_shape(NLD_prov) +
    	tm_borders(lwd=2) +
    	tm_text("name", shadow=TRUE) +
    tm_format("NLD", title="Dutch provinces and\nmunicipalities", bg.color="white")
}