New release of `maplegend`: version 0.4.0

maplegend

mapsf

Author

Timothée Giraud

Published

December 5, 2025

maplegend is a low/no dependency package for creating legends for maps and other graphics.
It is the backend used by mapsf for legend-related tasks.

The main improvement introduced by this release is the support for legends on plots of any aspect ratio.

The release introduces two new features: a new ‘histo’ legend type to create histogram legends, and new arguments to set decimal and big value separators.

Support for legends on plots of any aspect ratio

The functions of the package have been refactored to make them more robust and suitable for plots with asp != 1. This update is particularly beneficial for creating maps with unprojected layers (e.g. using EPSG:4326) in mapsf.

Code for the figures

png("legend.png", width = 800, height = 400, res = 110)
library(maplegend)
par(mfrow = c(1,3), mar = c(1,1.5,2,1.5))
plot.new()
plot.window(xlim = c(0, 1), ylim = c(0, 1), asp = 1)
box()
leg(type = "prop", val = c(10, 50, 100), pos = "topleft")
leg(type = "choro", val = c(10, 20, 30, 40, 50), pos = "left")
leg(type = "symb", val = c("A", "B", "C"), pos = "bottomleft")
title("Aspect ratio: 1")
plot.new()
plot.window(xlim = c(0, 1), ylim = c(0, 1), asp = .5)
box()
leg(type = "prop", val = c(10, 50, 100), pos = "topleft")
leg(type = "choro", val = c(10, 20, 30, 40, 50), pos = "left")
leg(type = "symb", val = c("A", "B", "C"), pos = "bottomleft")
title("Aspect ratio: 0.5")
plot.new()
plot.window(xlim = c(0, 1), ylim = c(0, 1), asp = 2)
box()
leg(type = "prop", val = c(10, 50, 100), pos = "topleft")
leg(type = "choro", val = c(10, 20, 30, 40, 50), pos = "left")
leg(type = "symb", val = c("A", "B", "C"), pos = "bottomleft")
title("Aspect ratio: 2")
dev.off()

New “histo” legend type

This new type uses an object of type histogram as input.

library(maplegend)
# Set dummy variables
set.seed(75)
x <- rnorm(1000) 
y <- rbeta(1000, .6, 7) * 1000
z <- rbeta(1000, 5, .6) * 1000
xh <- hist(x, breaks = quantile(x, probs = seq(0, 10, by = 2) / 10), plot = FALSE)
yh <- hist(y, breaks = quantile(y, probs = seq(0, 10, by = 2) / 10), plot = FALSE)
zh <- hist(z, plot = FALSE)
# Display and empty plot
plot.new()
plot.window(xlim = c(0, 1), ylim = c(0, 1))
box()
# Add 3 histogram legends
leg(type = "histo", val = xh, pos = "topleft")
leg(type = "histo", val = yh, pos = "left", box_cex = c(2, 2))
leg(type = "histo", val = zh, pos = "bottomleft")

I’ll probably add a parameter in mapsf to build these legends for choropleth maps:

Code for the figure

plot.new()
plot.window(xlim = c(0, 1), ylim = c(0, 1))
leg_comp(type = "choro", val = xh$breaks, pal = "Burg", val_rnd = 1, horiz = TRUE) |>
  leg_comp(type = "histo", val = xh, pal = "Burg", title = "", val_rnd = 1, box_cex = c(2, 1)) |>
  leg_draw(pos = "topleft")
leg_comp(type = "choro", val = yh$breaks, pal = "Greens", horiz = TRUE) |>
  leg_comp(type = "histo", val = yh, pal = "Greens", title = "", box_cex = c(2, 1)) |>
  leg_draw(pos = "topright")
leg_comp(type = "choro", val = zh$breaks, pal = "Turku", horiz = TRUE, box_cex = c(.5, 1)) |>
  leg_comp(type = "histo", val = zh, pal = "Turku", title = "") |>
  leg_draw(pos = "bottom")

Decimal and big value separators

New argumentss val_big and val_dec have been added for legend types already using val_rnd, to select decimal and big values separators.
These two arguments will soon also be accessible through mapsf.

library(maplegend)
# Display and empty plot
plot.new()
plot.window(xlim = c(0, 1), ylim = c(0, 1))
# Display legends
leg(type = "prop", val = c(2.60, 12.89, 25.43, 45.71),
    pos = "topleft", val_rnd = 2, val_cex = .8, 
    title = 'Decimal separator: ","',
    val_dec = ",")
leg(type = "choro", val = c(1526, 12620, 100000, 1000000, 10456000), 
    pos = "topright", val_cex = .7, 
    title = 'Big values separator: " "',
    val_big = " ")

See the NEWS file for the complete list of changes.