Beautiful maps with R (III): Patterns and hatched maps

In this post, I show how to produce different filling patterns that can be added over your shapefiles with the cartography package.

Historical example: The mapping examples use cartography, which is now in maintenance mode. Its maintainers recommend mapsf for new work. The original code and outputs are preserved and have not been revalidated against current package versions.

Updated 17 February 2020: All these pieces of work are already available in cartography >v.2.4.0 through the hatchedLayer and legendHatched functions. Just install it via install.packages("cartography"). A dedicated blog post with examples is available in this post.

Required R packages

library(sf)
library(dplyr)
library(giscoR)
library(cartography)

DE <- gisco_get_countries(country = "Germany", epsg = 3857)

Let's see how it works.

par(
  mfrow = c(3, 4),
  mar = c(1, 1, 1, 1),
  cex = 0.5
)
hatchedLayer(DE, "dot")
title("dot")
hatchedLayer(DE, "text", txt = "Y")
title("text")
hatchedLayer(DE, "diamond", density = 0.5)
title("diamond")
hatchedLayer(DE, "grid", lwd = 1.5)
title("grid")
hatchedLayer(DE, "hexagon", col = "blue")
title("hexagon")
hatchedLayer(DE, "horizontal", lty = 5)
title("horizontal")
hatchedLayer(DE, "vertical")
title("vertical")
hatchedLayer(DE, "left2right")
title("left2right")
hatchedLayer(DE, "right2left")
title("right2left")
hatchedLayer(DE, "zigzag")
title("zigzag")
hatchedLayer(DE, "circle")
title("circle")

Let's play a little bit more with some of the additional features of the function:

par(mar = c(1, 1, 1, 1), mfrow = c(2, 3))
plot(st_geometry(DE))
hatchedLayer(
  DE,
  "dot",
  pch = 10,
  density = 0.5,
  cex = 2,
  col = "darkblue",
  add = T
)
plot(st_geometry(DE))
hatchedLayer(
  DE,
  "dot",
  pch = 21,
  col = "red",
  bg = "green",
  cex = 1.25,
  add = T
)
plot(st_geometry(DE), col = "grey")
hatchedLayer(
  DE,
  "text",
  txt = "DE",
  density = 1.1,
  col = "white",
  add = T
)
plot(st_geometry(DE), col = "blue")
hatchedLayer(
  DE,
  "horizontal",
  lty = 3,
  cellsize = 150 * 1000,
  add = T
)
hatchedLayer(DE, "zigzag", lwd = 2, col = "red")
plot(st_geometry(DE), border = "orange", lwd = 2)
hatchedLayer(DE,
  "left2right",
  density = 2,
  col = "orange",
  add = T
)

Adding legends: the legendHatched function

As a complementary function, there is also legendHatched. The main parameters are:

• pos, title.txt, title.cex, values.cex, categ, cex and frame: See ?cartography::legendTypo.
• patterns: Vector of patterns to be created for each element on categ.
• ptrn.bg: Background of the legend box for each categ.
• ptrn.text: Text to be used for each categ="text", as a single value or a vector.
• dot.cex: cex of each categ="dot", as a single value or a vector.
• text.cex: Text size of each categ="text", as a single value or a vector.
• As in the case of the hatchedLayer function, different graphical parameters can be passed (lty, lwd, pch, bg on points).

Note that it is also possible to create solid legends by setting col and ptrn.bg to the same color. Parameters respect the order of the categ variable.

par(mar = c(0, 0, 0, 0), mfrow = c(1, 1))
plot(st_geometry(DE)) # Null geometry
legendHatched(
  title.txt = "Example 1",
  categ = c("a", "b"),
  patterns = "dot",
  pch = c(16, 23),
  frame = T
)
legendHatched(
  pos = "left",
  title.txt = "Example 2",
  categ = c("c", "d", "other text"),
  patterns = c("text", "zigzag"),
  ptrn.text = c("s", "pp"),
  ptrn.bg = "grey80",
  col = c("red", "blue")
)

legendHatched(
  pos = "topright",
  title.txt = "Example 3",
  categ = c("e", "f", "solid"),
  patterns = c("circle", "left2right"),
  ptrn.bg = c("orange", "yellow", "green"),
  col = c("white", "white", "green"),
  lty = c(2, 4),
  lwd = c(1, 3)
)


legendHatched(
  pos = "bottomright",
  title.txt = "Example 4",
  values.cex = 1.2,
  categ = c("h", "i", "j", "k"),
  patterns = c("grid", "diamond", "horizontal", "dot"),
  cex = 2,
  pch = 22,
  col = "white",
  ptrn.bg = "black",
  bg = "pink"
)

I hope that you find these functions useful. Enjoy, and happy mapping!