How to Get the Zoom Level from the Leaflet Map in R/Shiny

How to get the zoom level from the leaflet map in R/shiny?

You can access the zoom level using input$mapid_zoom (see here).

In your observe, you could do:

 observe({
                sel_site <- df[df$site == input$site,]
                isolate({
                        new_zoom <- 4
                        if(!is.null(input$map_zoom)) new_zoom <- input$map_zoom
                        leafletProxy('map') %>%
                                setView(lng = sel_site$lng, lat = sel_site$lat, zoom = new_zoom)
                })
        })

setting the zoom level to 7.25 in shiny leaflet r

Use leaflet map options:

• zoomSnap: how small you can define the zoom level.
• zoomDelta: how much the view zooms when clicking zoom control buttons

leaflet(options = leafletOptions(zoomSnap = 0.25, zoomDelta=0.25)) %>%
  addTiles()%>%
  setView(lng=-82.706838, lat=40.358615, zoom=7.25)

R Shiny Leaflet How to Change Circles Size Based on Zoom Level

Alright, this ended up being more involved than I thought but I finally got it to work. There is an observer that is the key. I also had to learn what leafletProxy() is (research it if you don't know). Finally, clearing the shapes with clearShapes() in the observer was key to getting this working when zooming both in and out. See code below.

## app.R ##
library(leaflet)
library(shinydashboard)
library(shinydashboardPlus)
library(dplyr)
ui <- dashboardPage(
  dashboardHeader(title = "Basic dashboard"),
  dashboardSidebar(),
  dashboardBody(
    leafletOutput("map", width = "100%", height = "500px")
    
  )
)

server <- function(input, output,session) {
  
  df <- data.frame("Lat"=c(32.921821,32.910853,32.793803,32.995084,32.683745,32.759999,32.800652,32.958861,32.835963,32.762578,32.649651,32.862843,32.862217,32.936876,32.963381),
                   "Long"=c(-96.840609,-96.738831,-96.689232,-96.857858,-96.825345,-96.684475,-96.794144,-96.816111,-96.676371,-96.897331,-96.944426,-96.754719,-96.856976,-96.752718,-96.770249))
  
  observeEvent(
    eventExpr = input$map_zoom, {
      print(input$map_zoom)           # Display zoom level in the console
      leafletProxy(
        mapId = "map", 
        session = session
      )%>% clearShapes() %>%
        addCircles(data=df,lng = ~Long, lat = ~Lat, 
                   weight = case_when(input$map_zoom <=4 ~1, 
                                      input$map_zoom ==5 ~2, 
                                      input$map_zoom ==6 ~3, 
                                      input$map_zoom ==7 ~5, 
                                      input$map_zoom ==8 ~7, 
                                      input$map_zoom ==9 ~9, 
                                      input$map_zoom >9 ~11),
                   opacity = 1, fill = TRUE, fillOpacity = 1 )
    }
  )
  
  output$map <- renderLeaflet({
    leaflet() %>%
      addTiles(urlTemplate = "//{s}.tiles.mapbox.com/v3/jcheng.map-5ebohr46/{z}/{x}/{y}.png",
               attribution = 'Maps by <a href="http://www.mapbox.com/">Mapbox</a>') %>%
      setView(lng = -96.84, lat = 32.92, zoom = 6) 
  })
}
shinyApp(ui, server)

shiny leaflet display labels based on zoom level

A few remarks on your code if you like.
If you wrap the zoom in a reactive function, reference it like mapscale(). Use the normal if statement in R and the ~ in front of the variable. Then you should be fine.

Reproducible example:

library(shiny)
library(leaflet)

df <- data.frame(
  location_name = c('S1', 'S2'),
  lng = c(-1.554136,  -2.10401),
  lat = c(47.218637, 47.218637), 
  stringsAsFactors = FALSE
)

ui <- shinyUI(
  fluidPage(
    leafletOutput(outputId = 'map')
  )
)

server <- shinyServer(function(input, output, session) {

  output$map <- renderLeaflet({
    leaflet() %>%
      addTiles()
  })

  observeEvent(
    eventExpr = input$map_zoom, {
      print(input$map_zoom)           # Display zoom level in the console
      leafletProxy(
        mapId = "map", 
        session = session
      ) %>% 
        clearMarkers() %>%
        addMarkers(
          data = df, 
          lng = ~lng,
          lat = ~lat,
          label = if(input$map_zoom < 6) ~location_name
      )
    }
  )

})

shinyApp(
  ui = ui, 
  server = server
)

In shiny, how to fix (lock) leaflet map view zoom and center?

You were nearly there. There is just one mistake in you app:

You'll need to change

center <- reactive({
    ifelse(is.null(input$map01_bounds),
           c(179.462, -20.64275),
           c((input$map01_bounds$bounds$north + input$map01_bounds$bounds$south)/2.0, 
             (input$map01_bounds$bounds$east + input$map01_bounds$bounds$west)/2.0))
  })

to

      center <- reactive({

        if(is.null(input$map01_center)){
          return(c(179.462, -20.64275))
          }else{
            return(input$map01_center)
        }

  })

The first reason being the ifelse does not work when length of vector more than 1 and second is that input$map01_center gives you the center.

Hope it helps!

Shiny leaflet display point weight based on zoom level breaks down when using if-else statement

Try case_when as

weight = case_when(input$map_zoom <=8 ~2, input$map_zoom >8 ~3)

This works fine for me:

observeEvent(eventExpr = input$mymap_zoom, {
      print(input$mymap_zoom)           # Display zoom level in the console
      mywt <- case_when(input$mymap_zoom <=8 ~1, input$mymap_zoom >8 ~6)
      print(mywt)
      leafletProxy(
        mapId = "mymap" , session = session
      )%>%
        clearShapes() %>% 
        addCircles(data=df,lng = ~Long, lat = ~Lat,
                   weight = mywt ,
                   opacity = 1, fill = TRUE, fillOpacity = 1 )
    }
  )

You just need clearShapes()

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