insetplot

insetplot is an R package to create ggplot2 maps with inset maps easily and flexibly. It handles spatial configuration, aspect ratios, and plot composition automatically.

Quick start

Approach 1: Reuse one plot (simplest)

Use the same plot for the main map and all insets — let insetplot handle sizing and positioning.

library(insetplot)
library(sf)
library(ggplot2)

# Load data
nc <- st_read(system.file("shape/nc.shp", package = "sf"), quiet = TRUE)

# Configure insets: one main + one inset
config_insetmap(
  data_list = list(nc),
  specs = list(
    inset_spec(main = TRUE),
    inset_spec(
      xmin = -84, xmax = -75, ymin = 33, ymax = 37,
      loc = "left bottom", scale_factor = 0.5
    )
  )
)

# Compose
with_inset(
  ggplot(nc, aes(fill = AREA)) +
    geom_sf() +
    scale_fill_viridis_c() +
    theme_void()
)

Approach 2: Custom plot per subplot

Provide specific plots for the main and inset maps.

base_plot <- ggplot(nc, aes(fill = AREA)) +
  geom_sf() + scale_fill_viridis_c() + theme_void()

main_plot <- base_plot +
  ggtitle("Full North Carolina") 

inset_plot <- base_plot +
  ggtitle("Detail Region") 

config_insetmap(
  data_list = list(nc),
  specs = list(
    inset_spec(main = TRUE, plot = main_plot),
    inset_spec(
      xmin = -84, xmax = -75, ymin = 33, ymax = 37,
      loc = "left bottom", scale_factor = 0.5,
      plot = inset_plot
    )
  )
)

with_inset()  # plot argument optional when each spec has its own plot

Installation

devtools::install_github("fncokg/insetplot")

Documentation

Full documentation and more examples are available at insetplot package site.

Core functions

inset_spec() — Define bbox, position, and size for each subplot
- bbox: xmin, xmax, ymin, ymax
- position: loc (e.g., “left bottom”) or loc_left/loc_bottom in [0, 1]
- size: prefer scale_factor; or provide one of width/height
- plot: optional custom ggplot object
- main: exactly one spec must set main = TRUE
config_insetmap() — Build and store configuration
- data_list: list of sf objects
- specs: list of inset_spec()
- crs: target CRS (passed to coord_sf as crs)
- border_args: forwarded to map_border() for inset borders
with_inset() — Compose main plot with insets
- plot: single ggplot or list per spec (optional)
- .as_is: return the input plot as-is (skip inset composition)
- .return_details: return list(full, subplots, subplot_layouts, main_ratio)
ggsave_inset() — Save with the correct aspect ratio
- Provide one of width or height; the other is computed from main_ratio
- Optional ratio_scale for small adjustments (e.g., legends)
map_border() — Small theme to draw a rectangular border around plots

Further examples

Custom positioning and sizing

config_insetmap(
  data_list = list(nc),
  specs = list(
    inset_spec(main = TRUE),
    inset_spec(
      xmin = -84, xmax = -75, ymin = 33, ymax = 37,
      loc_left = 0.05, loc_bottom = 0.05,
      # Use width only; height auto-calculated to preserve aspect ratio
      width = 0.25
    )
  )
)

with_inset(base_plot)

Pass custom plots after configuration

config_insetmap(
  data_list = list(nc),
  specs = list(
    inset_spec(main = TRUE),
    inset_spec(
      xmin = -84, xmax = -75, ymin = 33, ymax = 37,
      loc = "left bottom", scale_factor = 0.5,
    )
  )
)

with_inset(list(main_plot, inset_plot))

Save with correct aspect ratio

ggsave_inset(
  "map_with_insets.png",
  plot = composed_plot,
  # `height` auto-calculated from `main_ratio`
  width = 12,
  dpi = 300
)

Debugging with detailed output

result <- with_inset(plot = my_plot, .return_details = TRUE)
# result$full, result$subplots, result$subplot_layouts, result$main_ratio