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.

Usage

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,
  labels = NULL,
  naLabel = "NA",
  labelStyle = "",
  className = "info legend leaflet-control",
  data = leaflet::getMapData(map),
  ...
)

addLegendQuantile(
  map,
  pal,
  values,
  title = NULL,
  labelStyle = "",
  shape = "rect",
  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",
  naLabel = "NA",
  between = " - ",
  data = leaflet::getMapData(map),
  ...
)

addLegendBin(
  map,
  pal,
  values,
  title = NULL,
  labelStyle = "",
  shape = "rect",
  orientation = c("vertical", "horizontal"),
  width = 24,
  height = 24,
  numberFormat = function(x) {
     format(round(x, 3), big.mark = ",", trim = TRUE,
    scientific = FALSE)
 },
  opacity = 1,
  fillOpacity = opacity,
  group = NULL,
  className = "info legend leaflet-control",
  naLabel = "NA",
  between = " - ",
  data = leaflet::getMapData(map),
  ...
)

addLegendFactor(
  map,
  pal,
  values,
  title = NULL,
  labelStyle = "",
  shape = "rect",
  orientation = c("vertical", "horizontal"),
  width = 24,
  height = 24,
  opacity = 1,
  fillOpacity = opacity,
  group = NULL,
  className = "info legend leaflet-control",
  naLabel = "NA",
  data = leaflet::getMapData(map),
  ...
)

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

the desired shape of the symbol, See availableShapes

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 if it is of length one; you can also provide a numeric vector as the pre-defined breaks

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

labels

labels

naLabel

the legend label for NAs in values

labelStyle

character string of style argument for HTML text

className

extra CSS class to append to the control, space separated

data

a data object. Currently supported objects are matrices, data frames, spatial objects from the sp package (SpatialPoints, SpatialPointsDataFrame, Polygon, Polygons, SpatialPolygons, SpatialPolygonsDataFrame, Line, Lines, SpatialLines, and SpatialLinesDataFrame), and spatial data frames from the sf package.

...

arguments to pass to addControl

opacity

opacity of the legend items

between

a separator between legend range labels

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$mag)
leaflet(quakes) %>%
  addTiles() %>%
  addCircleMarkers(
    lat = ~ lat,
    lng = ~ long,
    color = ~ binPal(mag),
    opacity = 1,
    fillOpacity = 1
  ) %>%
  addLegendBin(
    pal = binPal,
    position = 'topright',
    values = ~mag,
    title = 'addLegendBin',
    labelStyle = 'font-size: 18px; font-weight: bold;',
    orientation = 'horizontal'
  ) %>%
  addLegend(pal = binPal,
            values = quakes$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(
    data = quakes,
    pal = binPal,
    position = 'bottomleft',
    title = 'addLegendBin',
    group = 'Bin',
    values = ~mag
  ) %>%
  addLayersControl(
    baseGroups = c('Numeric Data', 'Quantile'),  overlayGroups = c('Bin'),
    position = 'bottomright'
  )