Add a color legend for a heatmap

Usage

addHeatmapLegend(
  map,
  values,
  colors = NULL,
  max = NULL,
  title = "Intensity",
  position = "bottomright",
  layerId = NULL,
  opacity = 1,
  ...
)

Arguments

map: a map widget object created from leaflet()
values: numeric intensity values. The legend goes from 0 to max, matching how Leaflet.heat colors intensity / max.
colors: a color palette name, a vector of colors, a colorNumeric function, or a WebGL gradientTexture name such as "skyline" or "OrRd". The default matches the Leaflet.heat blue-cyan-lime-yellow-red ramp.
max: upper end of the legend. Defaults to the maximum of values.
title: legend title
position: the position of the legend
layerId: the ID of the legend; subsequent calls to addLegend or addControl with the same layerId will replace this legend. The ID can also be used with removeControl.
opacity: legend opacity
...: additional arguments passed to addLegend

Examples

leaflet(quakes) %>%
  addProviderTiles(providers$CartoDB.DarkMatter) %>%
  addHeatmap(lng = ~long, lat = ~lat, intensity = ~mag) %>%
  addHeatmapLegend(values = quakes$mag, title = "Magnitude")