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Scale bars, north arrows and legends in GeoSpaX styles

map-furniture.Rd

Map furniture you can add to any ggplot map drawn with ggplot2::coord_sf() (every tidymapr map uses it), in the same styles as the GeoSpaX desktop app:

  • annotation_scale_bar(): a scale bar whose length is measured on the ground (great-circle metres across the panel) when the map is drawn, so it is right for longitude/latitude and projected maps and in every facet. Styles: "pill" (default; rounded bar, half dark), "checker" (alternating blocks), "line" (a bracket with the distance above) and "ruler" (ticks at 0, 1/4, 1/2, 3/4 and 1). Units: "metric", "imperial" or "both" (a second bar in miles).

  • annotation_north_arrow(): styles "needle" (default; two-tone needle in a ring), "compass", "rose" (eight-point compass rose) and "minimal".

  • map_legend(): puts the legend "right" (default), "bottom", "inside" a corner of the map, or removes it ("none"), and customises it as in GeoSpaX: title, renamed entries (labels), hidden legends (hide), frame, text, title and key sizes, columns, direction and reversed order.

plot_sites(), plot_geo(), plot_choropleth() and plot_bubble() take the same style names through their scale_bar, north_arrow and legend arguments.

Usage

annotation_scale_bar(
  style = c("pill", "checker", "line", "ruler"),
  location = c("bl", "br", "tl", "tr"),
  units = c("metric", "imperial", "both"),
  length = NULL,
  pad = 3,
  text_size = 8,
  data = NULL
)

annotation_north_arrow(
  style = c("needle", "compass", "rose", "minimal"),
  location = c("tr", "tl", "br", "bl"),
  size = 16,
  pad = 3,
  data = NULL
)

map_legend(
  position = c("right", "bottom", "inside", "none"),
  corner = c("tr", "tl", "br", "bl"),
  title = NULL,
  labels = NULL,
  hide = NULL,
  frame = TRUE,
  text_size = NULL,
  title_size = NULL,
  key_size = NULL,
  ncol = NULL,
  direction = NULL,
  reverse = FALSE
)

Arguments

style

Furniture style (see Description).

location

Corner: "bl" (bottom left), "br", "tl" or "tr".

units

Scale bar units: "metric", "imperial" or "both".

length

Optional fixed bar length, in metres (or miles when units = "imperial"). When NULL, a round length of about a fifth of the map width.

pad

Distance from the panel edge, in millimetres.

text_size

Text size in points: scale bar labels, or legend entries in map_legend().

data

Optional one-row data frame holding facet columns, to draw the furniture in one facet only.

size

North arrow size in millimetres.

position

Legend position: "right", "bottom", "inside" or "none".

corner

For position = "inside", the corner ("tr", "tl", "br" or "bl").

title

Legend title. NULL keeps the titles the plot already has.

labels

Rename legend entries: a named character vector, c(old = "new"), applied to every discrete legend (colour, fill, shape) that shows those entries.

hide

Aesthetics whose legend to hide, for example "size".

frame

Draw a white box with a thin border around the legend?

title_size

Legend title size in points.

key_size

Size of the legend keys in millimetres.

ncol

Number of columns of legend entries.

direction

"vertical" or "horizontal"; by default horizontal at the bottom and vertical elsewhere.

reverse

Reverse the order of legend entries?

Value

A ggplot2 layer (annotation_*()) or legend settings (map_legend()) to add to a plot with +.

Examples

library(ggplot2)
# North Carolina counties (real data shipped with sf)
nc <- sf::st_read(system.file("shape/nc.shp", package = "sf"), quiet = TRUE)
base <- ggplot(nc) + geom_sf(aes(fill = AREA)) + theme_tidymapr(grid = "none")
base +
  annotation_scale_bar(style = "checker", location = "bl") +
  annotation_north_arrow(style = "rose", location = "tr") +
  map_legend("bottom", title = "Area")


# Customised legend: renamed entries, two columns, larger keys
nc$size_class <- cut(nc$AREA, c(0, 0.08, 0.15, 0.25),
  labels = c("small", "medium", "large")
)
ggplot(nc) +
  geom_sf(aes(fill = size_class)) +
  theme_tidymapr(grid = "none") +
  map_legend("inside",
    corner = "bl", title = "County size",
    labels = c(small = "Small (< 0.08)", large = "Large (> 0.15)"),
    ncol = 1, key_size = 6, text_size = 9
  )


# Every style at once
base +
  annotation_scale_bar(style = "pill", location = "bl", units = "both") +
  annotation_scale_bar(style = "ruler", location = "br") +
  annotation_north_arrow(style = "needle", location = "tl") +
  annotation_north_arrow(style = "compass", location = "tr") +
  map_legend("none")