Add Customizable Color Legends to a 'leaflet' map widget

Functions for more control over the styling of 'leaflet' legends. The 'leaflet' map is passed through and the output is a 'leaflet' control so that the legends are integrated with other functionality of the API. Style the text of the labels, the symbols used, orientation of the legend items, and sizing of all elements.

addLegendNumeric(
  map,
  pal,
  values,
  title = NULL,
  shape = c("rect", "stadium"),
  orientation = c("vertical", "horizontal"),
  width = 20,
  height = 100,
  bins = 7,
  numberFormat = function(x) {     prettyNum(x, format = "f", big.mark = ",", digits =
    3, scientific = FALSE) },
  tickLength = 4,
  tickWidth = 1,
  decreasing = FALSE,
  fillOpacity = 1,
  group = NULL,
  className = "info legend leaflet-control",
  ...
)

addLegendQuantile(
  map,
  pal,
  values,
  title = NULL,
  labelStyle = "",
  shape = c("rect", "circle", "triangle", "plus", "cross", "diamond", "star",
    "stadium"),
  orientation = c("vertical", "horizontal"),
  width = 24,
  height = 24,
  numberFormat = function(x) {     prettyNum(x, big.mark = ",", scientific = FALSE,
    digits = 1) },
  opacity = 1,
  fillOpacity = opacity,
  group = NULL,
  className = "info legend leaflet-control",
  ...
)

addLegendBin(
  map,
  pal,
  values,
  title = NULL,
  labelStyle = "",
  shape = c("rect", "circle", "triangle", "plus", "cross", "diamond", "star",
    "stadium"),
  orientation = c("vertical", "horizontal"),
  width = 24,
  height = 24,
  opacity = 1,
  fillOpacity = opacity,
  group = NULL,
  className = "info legend leaflet-control",
  ...
)

addLegendFactor(
  map,
  pal,
  values,
  title = NULL,
  labelStyle = "",
  shape = c("rect", "circle", "triangle", "plus", "cross", "diamond", "star",
    "stadium"),
  orientation = c("vertical", "horizontal"),
  width = 24,
  height = 24,
  opacity = 1,
  fillOpacity = opacity,
  group = NULL,
  className = "info legend leaflet-control",
  ...
)

Arguments

map	a map widget object created from 'leaflet'
pal	the color palette function, generated from colorNumeric
values	the values used to generate colors from the palette function
title	the legend title, pass in HTML to style
shape	shape of the color symbols
orientation	stack the legend items vertically or horizontally
width	in pixels
height	in pixels
bins	an approximate number of tick-marks on the color gradient for the colorNumeric palette
numberFormat	formatting functions for numbers that are displayed e.g. format, prettyNum
tickLength	in pixels
tickWidth	in pixels
decreasing	order of numbers in the legend
fillOpacity	fill opacity of the legend items
group	group name of a leaflet layer group
className	extra CSS class to append to the control, space separated
...	arguments to pass to addControl
labelStyle	character string of style argument for HTML text
opacity	opacity of the legend items

Value

an object from addControl

Examples

library(leaflet)

data(quakes)

# Numeric Legend

numPal <- colorNumeric('viridis', quakes$depth)
leaflet() %>%
  addTiles() %>%
  addLegendNumeric(
    pal = numPal,
    values = quakes$depth,
    position = 'topright',
    title = 'addLegendNumeric (Horizontal)',
    orientation = 'horizontal',
    shape = 'rect',
    decreasing = FALSE,
    height = 20,
    width = 100
  ) %>%
  addLegendNumeric(
    pal = numPal,
    values = quakes$depth,
    position = 'topright',
    title = htmltools::tags$div('addLegendNumeric (Decreasing)',
    style = 'font-size: 24px; text-align: center; margin-bottom: 5px;'),
    orientation = 'vertical',
    shape = 'stadium',
    decreasing = TRUE,
    height = 100,
    width = 20
  ) %>%
  addLegend(pal = numPal, values = quakes$depth, title = 'addLegend')

# Quantile Legend
# defaults to adding quantile numeric break points

quantPal <- colorQuantile('viridis', quakes$mag, n = 5)
leaflet() %>%
  addTiles() %>%
  addCircleMarkers(data = quakes,
                   lat = ~lat,
                   lng = ~long,
                   color = ~quantPal(mag),
                   opacity = 1,
                   fillOpacity = 1
  ) %>%
  addLegendQuantile(pal = quantPal,
                    values = quakes$mag,
                    position = 'topright',
                    title = 'addLegendQuantile',
                    numberFormat = function(x) {prettyNum(x, big.mark = ',',
                    scientific = FALSE, digits = 2)},
                    shape = 'circle') %>%
  addLegendQuantile(pal = quantPal,
                    values = quakes$mag,
                    position = 'topright',
                    title = htmltools::tags$div('addLegendQuantile',
                                                htmltools::tags$br(),
                                                '(Omit Numbers)'),
                    numberFormat = NULL,
                    shape = 'circle') %>%
  addLegend(pal = quantPal, values = quakes$mag, title = 'addLegend')

# Factor Legend
# Style the title with html tags, several shapes are supported drawn with svg

quakes[['group']] <- sample(c('A', 'B', 'C'), nrow(quakes), replace = TRUE)
factorPal <- colorFactor('Dark2', quakes$group)
leaflet() %>%
  addTiles() %>%
  addCircleMarkers(
    data = quakes,
    lat = ~ lat,
    lng = ~ long,
    color = ~ factorPal(group),
    opacity = 1,
    fillOpacity = 1
  ) %>%
  addLegendFactor(
    pal = factorPal,
    title = htmltools::tags$div('addLegendFactor', style = 'font-size: 24px; color: red;'),
    values = quakes$group,
    position = 'topright',
    shape = 'triangle',
    width = 50,
    height = 50
  ) %>%
  addLegend(pal = factorPal,
            values = quakes$group,
            title = 'addLegend')

# Bin Legend
# Restyle the text of the labels, change the legend item orientation

binPal <- colorBin('Set1', quakes$mag)
leaflet() %>%
  addTiles() %>%
  addCircleMarkers(
    data = quakes,
    lat = ~ lat,
    lng = ~ long,
    color = ~ binPal(mag),
    opacity = 1,
    fillOpacity = 1
  ) %>%
  addLegendBin(
    pal = binPal,
    values = quakes$mag,
    position = 'topright',
    title = 'addLegendBin',
    labelStyle = 'font-size: 18px; font-weight: bold;',
    orientation = 'horizontal'
  ) %>%
  addLegend(pal = binPal,
            values = quakes$mag,
            title = 'addLegend')

# Group Layer Control
# Works with baseGroups and overlayGroups

leaflet() %>%
  addTiles() %>%
  addLegendNumeric(
    pal = numPal,
    values = quakes$depth,
    position = 'topright',
    title = 'addLegendNumeric',
    group = 'Numeric Data'
  ) %>%
  addLegendQuantile(
    pal = quantPal,
    values = quakes$mag,
    position = 'topright',
    title = 'addLegendQuantile',
    group = 'Quantile'
  ) %>%
  addLegendBin(
    pal = binPal,
    values = quakes$mag,
    position = 'bottomleft',
    title = 'addLegendBin',
    group = 'Bin'
  ) %>%
  addLayersControl(
    baseGroups = c('Numeric Data', 'Quantile'),  overlayGroups = c('Bin'),
    position = 'bottomright'
  )