Leaflet multiple provider tiles with lapply - r

Question

I would like to add OpenStreetMap, OpenTopoMap and Stamen.TonerLines in a list to a leaflet map.
I get those names with
library("leaflet"); library("leafem")
names(providers)[c(1,10,40)]
[1] "OpenStreetMap" "OpenTopoMap" "Stamen.TonerLines"
My map is this
n = leaflet() %>%
addTiles(group = "Base") %>%
setView( lng = 1, lat = 40, zoom = 5 )
n
My lapply code is this
lapply(
c(1,10,40),
function(i) addProviderTiles(map=n, names(providers)[i], layerId = i, group =names(providers)[i])
)
lapply(
c(1,10,40),
function(i) addLayersControl(map=n, baseGroups = names(providers)[i])
)
Now I have only last tile!
How could I add those tiles using lapply?

Answer 1

You could do something like this
n = leaflet() %>%
addTiles(group = "Base") %>%
setView( lng = 1, lat = 40, zoom = 5 )
n %>% addProviderTiles(providers$OpenStreetMap, group = 'OpenStreetMap') %>%
addProviderTiles(providers$OpenTopoMap, group='OpenTopoMap') %>%
addLayersControl(baseGroups = c('OpenStreetMap', 'OpenTopoMap'))
To wrap into a function calling index
layered_map <- function(..., provider=NULL, base_map_name="Base") {
select_providers <- provider[c(...)]
iter <- function(providers, layerid) {
if (length(providers)==0) {
leaflet() %>% addTiles(group = base_map_name) %>% setView(lng = 1, lat = 40, zoom = 5 )
} else {
iter(providers[-length(providers)], layerid-1) %>%
addProviderTiles(providers[[length(providers)]],
layerId = layerid,
group = providers[[length(providers)]])
}
}
controlnames <- if (length(select_providers)==0) base_map_name else names(select_providers)
iter(select_providers, length(select_providers)) %>% addLayersControl(baseGroups = controlnames)
}
To call the function:
library("leaflet")
library("leafem")
layered_map(1, 10, 40, provider=providers)
It is quite generic. So, if you want to generate a base map without additional layers. You could simply do
layered_map()
or
layered_map(base_map_name="My base map")
which will give you