Creating Interactive Leaflet Maps in RMarkdown with Hugo and HTMLTools

Interactive Leaflet Maps in RMarkdown: A Deep Dive into HTML Rendering and Hugo

Introduction

As data visualization becomes an essential aspect of modern data science, creating interactive visualizations has become a crucial skill for data analysts and scientists. One popular library for creating spatial data visualizations is the mapview package, which allows users to create interactive Leaflet maps in R. In this article, we will explore how to render these interactive maps in an RMarkdown document that can be knit into HTML using Hugo.

Background

RStudio provides a convenient way to create RMarkdown documents that can be easily shared or embedded in other documents. One of the features of RMarkdown is the ability to export visualizations as images, which can then be included in the final document. However, this approach has its limitations when it comes to interactive visualizations.

mapview, a popular package for creating spatial data visualizations, provides an easy-to-use interface for creating interactive Leaflet maps. When using purrr and mapview together, users can create multiple maps with different subsets of the data. However, rendering these interactive maps in HTML using Hugo requires some extra effort.

The Problem

The original problem statement describes a scenario where a user tries to plot spatial data on interactive Leaflet maps using mapview and purrr. When running the code in RStudio, the map is visible, but when knitting the HTML file, the map does not render interactively. This issue is likely due to the way Hugo renders HTML documents.

Solution Overview

To solve this problem, we need to understand how Hugo renders HTML documents and how to use the htmltools package to create interactive Leaflet maps in RMarkdown documents. The solution involves using htmltools::tagList() to render each map individually and then combining them into a single HTML document.

Step 1: Setting Up the Environment

Before we begin, let’s set up our environment by installing the required packages:

library('tidyverse')
library('sf')
library('mapview')
library('htmltools')

We also need to load the st_as_sf() function from the sf package, which is used to convert data frames into spatial data structures.

Step 2: Creating the Data

Next, let’s create a sample dataset using the data.frame() function:

df = data.frame(lon = 1:9,
                 lat = 1:9,
                 id = c(rep(1,5), rep(2,4))) %&gt;% 
      st_as_sf(coords = c("lon", "lat"), crs = 4326)

This dataset contains two columns (lon and lat) and one column (id) with repeated values.

Step 3: Splitting the Data

We can split the data into multiple datasets using the purrr::split() function:

df = split(df, df$id)

This will create separate subsets of the data for each value in the id column.

Step 4: Creating the Maps

Now we can use the purrr::set_names() and mapview functions to create interactive Leaflet maps for each subset of the data:

df_maps = df %&gt;% 
  purrr::set_names() %&gt;% 
  map(.x = .,
      .f = mapview)

This will create a list of maps, where each map corresponds to a single subset of the data.

Step 5: Adding HTML Headers

To render each map individually, we can use the htmltools::tagList() function:

df_maps =
  imap(.x = df_maps,
       .f = function(x, y) {
         list(h4(paste("Subset:", y)),
              x)
       }) %&gt;%
  flatten()

This will add an HTML header (h4) to each map with the corresponding subset name.

Step 6: Rendering the Maps

Finally, we can render the maps using tagList():

tagList(df_maps)

This will output a list of HTML tags, where each tag corresponds to a single map.

Conclusion

In this article, we explored how to create interactive Leaflet maps in RMarkdown documents that can be rendered as HTML using Hugo. We discussed the limitations of rendering visualizations as images and introduced htmltools::tagList() as a solution for rendering interactive maps individually. By following these steps, users can create interactive Leaflet maps in their RMarkdown documents with ease.

Additional Resources

For more information on how to use mapview and purrr, see the package documentation:

For more information on how to render interactive maps in RMarkdown documents using Hugo, see the following resources:

Last modified on 2024-01-25