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maplayer

The goal of maplayer is to provide a consistent set of functions for creating map layers using simple feature ({sf}) data, the {ggplot2} package, and a variety of ggplot2 extension packages.

Basic functions

The main layers that work with both a data and location sf object are:

There are several layers that can work with a single sf object as the input data:

Finally, there are layers that require additional packages (listed in Suggests):

The package also allows the optional use of packages designed for transforming spatial data or modifying ggplot2 maps. These include:

  • {smoothr} (required to use the smooth_params argument)
  • {ggfx} (required to use the shadow_params argument)

Many of the functions in {maplayer} were originally developed for the {overedge} package or before that for the {mapbaltimore} package. The {overedge} package has been split up into three smaller packages including {maplayer}, {getdata}, and {sfext}.

Installation

You can install the development version of maplayer like so:

pak::pkg_install("elipousson/maplayer")

Example 

library(maplayer)
library(ggplot2)
library(sf)
#> Linking to GEOS 3.11.0, GDAL 3.5.3, PROJ 9.1.0; sf_use_s2() is TRUE

Add icons to a map

layer_icon() wraps ggsvg::geom_point_svg() to provide an convenient way to make icon maps.

You can create maps using a single named icon that matches one of the icons in map_icons.

nc <- read_sf(system.file("shape/nc.shp", package = "sf"))
nc <- st_transform(nc, 3857)
theme_set(theme_void())

nc_map <-
  ggplot() +
  geom_sf(data = nc)

nc_map +
  layer_icon(data = nc, icon = "point-start", size = 8)

Add a neatline to a map

layer_neatline() hides major grid lines and axis label by default. The function is useful to draw a neatline around a map at a set aspect ratio.

nc_map +
  layer_neatline(
    data = nc,
    asp = "6:4",
    color = "gray60", linewidth = 2, linetype = "dashed"
  )

layer_neatline() can also be used to focus on a specific area of a map with the option to apply a buffer as a distance or ratio of the diagonal distance for the input data. The label_axes and hide_grid parameters will not override a set ggplot theme.

nc_map +
  layer_neatline(
    data = nc[1, ],
    diag_ratio = 0.5,
    asp = 1,
    color = "black",
    label_axes = "--EN",
    hide_grid = FALSE,
    expand = FALSE
  )

Add labels or numbers to a map 

nc_map +
  layer_labelled(
    data = nc[c(10, 20, 30, 40), ],
    geom = "sf_label",
    mapping = aes(label = NAME)
  )

nc_map +
  layer_numbers(
    data = nc[c(10, 20, 30, 40), ],
    aes(fill = NAME),
    num_style = "Alph",
    size = 3.5
  ) +
  guides(fill = "none")

Create a frame around a feature 

circle_nc <-
  ggplot(data = nc) +
  # layer_frame requires a data arg if neatline = TRUE
  layer_frame(data = nc, style = "circle") +
  # layer_location_data can inherit data
  layer_location_data()

circle_nc

Create an inset map 

nc_context <-
  layer_frame(
    data = nc,
    linetype = "twodash",
    neatline = FALSE,
    basemap = TRUE
  ) +
  layer_location_context(
    location = nc[25, ],
    context = nc,
    context_params = list(fill = "white", color = "gray80", alpha = 1),
    neatline = FALSE
  )

nc_context +
  layer_neatline(
    data = nc[25, ],
    dist = 15,
    unit = "mi",
    asp = 1
  ) +
  layer_inset(
    inset = nc_context,
    scale = 1.5
  )