Leaflet Zoom Observer

[Charles Youds]

Hey guys! I'm writing an RShiny Leaflet app (using MLS real-estate data), but I'm having trouble detecting a zoom event on the map. Here's what I have so far:

myMap <- reactive({

    return(

      leaflet(mls) %>%

        addControlFullScreen() %>%

        addProviderTiles("CartoDB.Positron", options = providerTileOptions(noWrap = TRUE)) %>%

        addDrawToolbar(polyline = FALSE, marker = FALSE) %>%

        addCircleMarkers(

          group = "marker",

          label =  ~ mls$address,

          lat = ~ geo.latitude,

          lng = ~ geo.longitude,

          stroke = FALSE,

          fillOpacity = 0.5,

          color = "coral",

          radius = 5

        ) %>%

        addSearchMarker("marker", position = "topleft", propertyName = "label") %>%

        addControlGPS()

    )

 })

  output$mymap <- renderLeaflet({

    myMap()

  })

  

  # A reactive expression that returns the set of mls locations that are in bounds right now

  mlsInBounds <- reactive({

    if (is.null(input$mymap_bounds))

      return(mls[FALSE, ])

    bounds <- input$mymap_bounds

    latRng <- range(bounds$north, bounds$south)

    lngRng <- range(bounds$east, bounds$west)

    subset(

      mls,

      geo.latitude >= latRng[1] & geo.latitude <= latRng[2] &

      geo.longitude >= lngRng[1] & geo.longitude <= lngRng[2]

    )

  })

  

  output$scatterMlsMap <- renderPlot({

    # If no listings are in view, don't plot

    if (nrow(mlsInBounds()) == 0)

      return(NULL)

    print(

      xyplot(

        floor.area.grand.total ~ list.price,

        data = mlsInBounds(),

        xlim = range(mls$floor.area.grand.total),

        ylim = range(mls$list.price)

      )

    )

  })

This is the relevant code. When I call

observeEvent(input$mymap_bounds,{ print("bounds changed") })

it only gets called when the map is opened. The goal is to have a scatterplot that gets generated based on the MLS listings that are within bounds.

[Joe Cheng]

That should work. Do you see any errors in your browser's JavaScript console?

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[Charles Youds]

On Thursday, June 9, 2016 at 12:05:00 PM UTC-7, Joe Cheng [RStudio] wrote:

That should work. Do you see any errors in your browser's JavaScript console?

Sadly no errors! It prints my output: "bounds changed" twice, and that's it. :(

[Joe Cheng]

Hmm, I don't know. The following works. Can you try narrowing it to a minimal reproducible example (as well as indicating the branch you used to install leaflet)? Thanks...

library(shiny)

library(leaflet)

ui <- fluidPage(

  leafletOutput("mymap")

)

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

  output$mymap <- renderLeaflet({

    leaflet() %>% addTiles()

  })

  

  observeEvent(input$mymap_bounds, {

    print("Bounds changed")

  })

}

shinyApp(ui, server)

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[Charles Youds]

I should have done that earlier. I apologize.

I ran the code snippet you posted as its own separate file, and zooming still didn't change the bounds.

Tried installing a fresh version of Leaflet, and that fixed it. Previously, I was using ("ssoulier/leaflet") and I guess it's out of date. Thank you very much! :D