Add UI controls to switch layers on and off

Description

Uses Leaflet's built-in layers control feature to allow users to choose one of several base layers, and to choose any number of overlay layers to view.

Usage

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addLayersControl(map, baseGroups = character(0), overlayGroups = character(0), 
    position = c("topright", "bottomright", "bottomleft", "topleft"), 
    options = layersControlOptions())

layersControlOptions(collapsed = TRUE, autoZIndex = TRUE)

removeLayersControl(map)

Arguments

map

the map to add the layers control to

baseGroups

character vector where each element is the name of a group. The user will be able to choose one base group (only) at a time. This is most commonly used for mostly-opaque tile layers.

overlayGroups

character vector where each element is the name of a group. The user can turn each overlay group on or off independently.

position

position of control: 'topleft', 'topright', 'bottomleft', or 'bottomright'

options

a list of additional options, intended to be provided by a call to layersControlOptions

collapsed

if TRUE (the default), the layers control will be rendered as an icon that expands when hovered over. Set to FALSE to have the layers control always appear in its expanded state.

autoZIndex

if TRUE, the control will automatically maintain the z-order of its various groups as overlays are switched on and off.

Examples

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leaflet() %>% addTiles(group = "OpenStreetMap") %>% addProviderTiles("Stamen.Toner", 
    group = "Toner by Stamen") %>% addMarkers(runif(20, -75, -74), runif(20, 
    41, 42), group = "Markers") %>% addLayersControl(baseGroups = c("OpenStreetMap", 
    "Toner by Stamen"), overlayGroups = c("Markers"))