leafcirclelegend

Add scaled circle legends to leaflet maps.

Installation

You can install the development version of leafcirclelegend using the remotes package`:

remotes::install_github("epicentre-msf/leafcirclelegend")

Example

Setup

library(tidyverse)
library(leaflet)
library(leafcirclelegend)

data("quakes")

# take a sample of the data for example purposes
df_leaf <- slice_sample(quakes, n = 20) %>% arrange(desc(depth))

# make a scaling function to convert real numbers to radii appropriate for leaflet
calc_radius <- function(n, scale_factor = 30) {
  sqrt(n) / sqrt(max(n)) * scale_factor
}

# define stroke and fill params
stroke_color <- "#FFFFFF"
stroke_weight <- 1
fill_color <- "#e06e22"
fill_opacity <- 0.7

Map

leaflet(df_leaf) %>% 
  addTiles() %>% 
  addLayersControl(
    overlayGroups = "Circles", 
    position = "topleft",
    options = layersControlOptions(collapsed = FALSE)
  ) %>% 
  addCircleMarkers(
    lng = ~long, 
    lat = ~lat, 
    radius = ~calc_radius(depth),
    label = ~depth,
    fillColor = fill_color, 
    fillOpacity = fill_opacity, 
    weight = stroke_weight, 
    color = stroke_color,
    group = "Circles"
  ) %>% 
  addCircleLegend(
    title = "Quake Depth",
    values = ~depth,
    scaling_fn = calc_radius,
    fillColor = fill_color, 
    fillOpacity = fill_opacity, 
    weight = stroke_weight, 
    color = stroke_color,
    position = "topright",
    group = "Circles"
  )

Related Projects

The leaflegend package provides many additional legend options for leaflet maps, but does not have a scaled circle option in the style of this package. Some code, most notably the javascript code to add the legend to a group that can be controlled by a layer control, was taken from leaflegend.