Embedding a Map Using the inset_element() Function from the Patchwork Package in R

In recent versions of the patchwork package, a new function called inset_element() has been introduced for embedding maps within larger maps. This feature offers users the ability to create visually appealing and informative spatial visualizations by integrating smaller maps into their existing work. In this article, we will explore how to effectively use the inset_element() function from the patchwork package in R to embed a map.

Overview of the Patchwork Package

The patchwork package is designed for combining multiple plots into a single panel or patchwork layout. This allows users to create complex and visually appealing spatial visualizations by integrating different types of maps, charts, and graphics into their work.

Installing the Patchwork Package

Before we can use the inset_element() function, we need to ensure that the patchwork package is installed in our R environment. We can install it using the following command:

install.packages("patchwork")

Importing Necessary Libraries and Loading Data

To begin working with maps and patchwork layouts, we need to load several essential libraries. These include ggplot2, rnaturalearth, sf (the SF package), and others.

library(patchwork)
library(sf)
library(ggplot2)
library(rnaturalearth)
world <- rnaturalearth::ne_countries(scale='medium',returnclass = 'sf')
p1 <- ggplot() + geom_sf(data= world)

Understanding the Error

When we try to create a patchwork object with inset_element() and use it to embed a map within another larger map, we encounter an error. This error occurs due to how R generates dimensions for patches.

p2 <- ggplot() + 
  geom_point(data = iris, aes(x= Petal.Width, y = Petal.Length))

# Try embedding p1 in the inset of p2
fail <- p2 + inset_element(p1, left =0.75, right =0.95, bottom = 0.75, top =0.95)

# Print fail to see the error message
fail

Resolving the Error

We can work around this issue by explicitly setting the layout dimensions of the patches object to be infinite for both width and height.

# Set layout dimensions for patches
fail$patches$layout$widths <- 1
fail$patches$layout$heights <- 1

# Print fail with corrected dimensions
fail

This approach allows us to successfully create a patchwork object where we can embed smaller maps into larger ones.

Embedding Maps Using inset_element()

Now that we have resolved the error and set up our working environment, let’s delve deeper into how inset_element() functions and explore some best practices for using this function effectively in your R projects.

Example 1: Embedding One Map Within Another

Let’s start with a basic example where we embed one map within another. In this case, we will use p1 (a world map) as the main map and embed p2 (an iris map) within it.

# Create patchwork object p3 with inset_element()
p3 <- p1 + inset_element(p2, left =0.75, right =0.95, bottom = 0.75, top =0.95)

Example 2: Embedding a Map as “Main” or “Inset”

We can control the position of an embedded map by using different settings for left, right, bottom, and top. Here we demonstrate how to embed one map as both the main element and as an inset.

# Embed p2 as the main element
p1 + inset_element(p2, left =0.75, right =0.95, bottom = 0.75, top =0.95)

# Embed p1 as the "inset"
p2 + inset_element(p1, left =0.75, right =0.95, bottom = 0.75, top =0.95)

Conclusion

In this article, we explored how to use the inset_element() function from the patchwork package in R to embed maps within larger maps. We discussed common challenges associated with using inset_element(), such as errors due to dimension generation issues. By understanding these challenges and implementing simple solutions like setting layout dimensions for patches, we can effectively integrate smaller maps into our spatial visualizations.

Practice Time

With the knowledge gained in this article, try creating your own map embedding projects! Remember to explore different inset_element() settings to control where you place embedded maps within larger panels.

Last modified on 2024-11-06