Display layers at certain zoom levels in R Leaflet

问题

I am working on an interactive map with the R package "leaflet".

I would like to change automatically the visible layers depending on the zoom level.

For example, I would like to have a polygon layer disappearing when zooming in, replaced by a points layer. Something like this : https://tree-map.nycgovparks.org/

I've been trying many different tricks and exploring in details the help from the "leaflet" and "leaflet.extras" packages, but could not find anything doing that.

I also found something straight from leaflet but it does not seem to be reproducible under R : Setting zoom level for layers in leaflet

I tried to use the options minZoom and maxZoom from markerOptions, but it does not appear to do what I want.

Here is my code for this example :


require(spData)
require(leaflet)
require(sf)

# loading shapes of countries from the package spData

data(world)
world <- st_read(system.file("shapes/world.gpkg", package="spData"))

# creating a sf objet with oceanian countries boundaries

oceania <- world[world$continent=="Oceania",]

#loading points events from the quakes dataset

data(quakes)

#Creating a leaflet objet with points and polygons

leaflet() %>%
  addProviderTiles(providers$CartoDB.Positron) %>%
  addCircleMarkers(lng=quakes$long,
                   lat=quakes$lat,
                   col="blue",
                   radius=3,
                   stroke=FALSE,
                   fillOpacity = 0.7,
                   options = markerOptions(minZoom=15, maxZoom=20)) %>%
  addPolygons(data= oceania,
              col="red")

It gives me the expected layers with the expected background from openstreetmap, but the minZoom and maxZoom arguments don't change anything. I expected the points layer to only appear between zoom levels 15 and 20, but it does not work like this, it seems.

Image from the viewer

回答1:

The group argument in most of the "addElement()" type functions becomes very important for managing how a map works. I recommend it, and you can do a lot of neat stuff by carefully thinking about how you group your data.

By calling groupOptions(), you can set the zoom levels for whatever layers you like. Below I have added the zoom levels you specified, but feel free to play around with it to adjust it to your needs.

#Creating a leaflet object with points and polygons

leaflet() %>%
  addProviderTiles(providers$CartoDB.Positron) %>%
  addCircleMarkers(lng=quakes$long,
                   lat=quakes$lat,
                   col="blue",
                   radius=3,
                   stroke=FALSE,
                   fillOpacity = 0.7,
                   #options = markerOptions(minZoom=15, maxZoom=20), # Oldcode
                   group = "Quake Points") %>%                       # Newcode
  addPolygons(data= oceania,
              col="red") %>%                        
  groupOptions("Quake Points", zoomLevels = 15:20)                   # Newcode

来源：https://stackoverflow.com/questions/61503281/display-layers-at-certain-zoom-levels-in-r-leaflet

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