Add a legend to a map for a specific layer

Usage

add_legend(
  map,
  layer_id,
  title = NULL,
  values = NULL,
  colours = NULL,
  options = list()
)

Arguments

map: A toro map or map proxy object.
layer_id: The ID of the layer to which the legend should be associated.
title: Optional title for the legend.
values: Optional vector of values to be displayed in the legend.
colours: Optional vector of colours corresponding to the values in the legend.
options: Optional list of additional legend options (e.g., position, orientation).

Value

The modified map object with the added legend.

Examples

library(shiny)
library(dplyr)
library(sf)
library(toro)

data(quakes)
quakes_data <- quakes |>
  dplyr::mutate(
    description = paste(
      "<div class='map-popup'>Location:",
      lat,
      ",",
      long,
      "<br>",
      "Magnitude:",
      mag,
      "</div>"
    )
  ) |>
  sf::st_as_sf(coords = c("long", "lat"), crs = 4326, remove = FALSE)


ui <- fluidPage(
  toro::mapOutput("map"),
  div(
    class = "row",
    checkboxInput(
      "include_quakes_legend",
      "Include earthquakes magnitude legend",
      value = TRUE
    ),
    checkboxInput(
      "include_quakes_lat_legend",
      "Include earthquakes latitude legend",
      value = TRUE
    )
  )
)

colours <- c(
  "#440154FF",
  "#414487FF",
  "#2A788EFF",
  "#22A884FF",
  "#7AD151FF",
  "#FDE725FF"
)

server <- function(input, output, session) {
  # Render UI -------------------------------------------------------

  output$map <- toro::renderMap({
    toro::map() |>
      set_zoom(3) |>
      add_circle_layer(
        id = "quakes",
        source = quakes_data,
        hover_column = "description",
        paint = get_paint_options(
          "circle",
          options = list(
            color = get_column_steps(
              "mag",
              breaks = quantile(quakes_data$mag),
              values = colours
            )
          )
        )
      ) |>
      add_circle_layer(
        id = "quakes_lat",
        source = quakes_data,
        hover_column = "description",
        paint = get_paint_options(
          "circle",
          options = list(
            color = get_column_steps(
              "lat",
              breaks = quantile(quakes_data$lat),
              values = colours
            )
          )
        )
      ) |>
      add_legend(
        title = "Earthquake magnitude",
        layer_id = "quakes"
      ) |>
      add_legend(
        title = "Earthquake latitude",
        layer_id = "quakes_lat"
      ) |>
      add_layer_selector_control(
        layer_ids = c("quakes", "quakes_lat"),
        position = "top-left"
      )
  })

  # Observers -------------------------------------------------------------

  observe({
    req(input$map_loaded)
    if (input$include_quakes_legend == TRUE) {
      toro::mapProxy("map") |>
        add_legend(
          title = "Earthquake magnitude",
          layer_id = "quakes"
        )
    } else {
      toro::mapProxy("map") |>
        remove_legend(layer_id = "quakes")
    }
  }) |>
    bindEvent(input$include_quakes_legend)

  observe({
    req(input$map_loaded)
    if (input$include_quakes_lat_legend == TRUE) {
      toro::mapProxy("map") |>
        add_legend(
          title = "Earthquake latitude",
          layer_id = "quakes_lat"
        )
    } else {
      toro::mapProxy("map") |>
        remove_legend(layer_id = "quakes_lat")
    }
  }) |>
    bindEvent(input$include_quakes_lat_legend)
}

if (interactive()) {
  shinyApp(ui, server)
}