How to show/hide legend with control layer panel with leaflet? - r

Question

I am trying to plot a map with multiple layers. However, when selecting the group I want to show in the controlLayer panel, it changes the map but not the legend. In fact, the 2 legends are always displayed together on the map, but I only want one of them at a time.
Here is the code I use :
leaflet(data) %>%
addProviderTiles("Esri.WorldStreetMap") %>%
addRasterImage(r, opacity = 1, colors = cb, group = "Predictions") %>%
addLegend(pal = cb, values = wind_speed_range, title = "Wind Speed", opacity = 1, group = "Predictions", position = "topright") %>%
addCircles(radius = ~ residual*7000, color = "black", fillColor = ~ cb(predictions), fillOpacity = 1, label = ~ paste(as.character(residual), " / ", as.character(vitesse_vent), " / ", as.character(predictions)), weight = 2, group = "Predictions") %>%
addRasterImage(raster_difference, opacity = 1, colors = cb_correction, group = "Corrections") %>%
addLegend(pal = cb_correction, values = correction_range, title = "Corrections", opacity = 1, group = "Corrections", position = "topright") %>%
addLayersControl(
baseGroups = c("Prédictions", "Corrections"),
options = layersControlOptions(collapsed = FALSE),
position = "topleft"
)
As you can see, I already tried the solution of this post. I also tried with overlayGroup instead of baseGroup, but the problem is still here.
The image below is what I get using this code :
You can clearly see the two legends.

Answer 1

Code
Unfortunately, you did not provide a reprex, so I show it with a made up example:
library(leaflet)
cities1 <- data.frame(City = factor(c("Boston", "Hartford",
"New York City", "Philadelphia", "Pittsburgh", "Providence")),
Lat = c(42.3601, 41.7627, 40.7127, 39.95, 40.4397, 41.8236),
Long = c(-71.0589, -72.6743, -74.0059, -75.1667, -79.9764, -71.4222),
Pop = c(645966L, 125017L, 8406000L, 1553000L, 305841L, 177994L),
Type = factor(c("C", "D", "A", "A", "B", "C")))
cities2 <- data.frame(City = factor(c("Baltimore", "Ithaca", "Wareham")),
Lat = c(39.299236, 42.443962, 41.761452),
Long = c(-76.609383, -76.501884, -70.719734),
Pop = c(609032L, 30569L, 22666L),
Type = factor(letters[1:3]))
pal1 <- colorFactor("viridis", domain = cities1$Type)
pal2 <- colorFactor("Set1", domain = cities2$Type)
leaflet(cities1) %>%
addTiles() %>%
addCircles(data = cities1, lng = ~Long, lat = ~Lat, weight = 1, group="one",
radius = ~sqrt(Pop) * 30, popup = ~City, color = ~pal1(Type), opacity = .9
) %>%
addLegend(pal = pal1, values = ~Type, group = "one", layerId = "one") %>%
addCircles(data = cities2, lng = ~Long, lat = ~Lat, weight = 1, group = "two",
radius = ~sqrt(Pop) * 30, popup = ~City, color = ~pal2(Type), opacity = .9
) %>%
addLegend(pal = pal2, values = ~Type, data = cities2, group = "two", layerId = "two") %>%
addLayersControl(
baseGroups = c("one", "two"),
options = layersControlOptions(collapsed = FALSE),
position = "topleft"
) %>%
htmlwidgets::onRender("
function() {
var map = this;
var legends = map.controls._controlsById;
function addActualLegend() {
var sel = $('.leaflet-control-layers-base').find('input[type=\"radio\"]:checked').siblings('span').text().trim();
$.each(map.controls._controlsById, (nm) => map.removeControl(map.controls.get(nm)));
map.addControl(legends[sel]);
}
$('.leaflet-control-layers-base').on('click', addActualLegend);
addActualLegend();
}")
Explanation
You can define some custom JavaScript which reacts upon the changes of the radio buttons. When they change, I basically delete all controls and add the selected. In order for this to work, I need to save a copy of the controls first. This is of course a bit hackish (especially since I am accessing the "private" _controlsById slot of the map), but from my quick scan of the leaflet API I did not find a better entry point.
Screenshot