Is drill-down in choropleth maps possible?

[pssguy]

If I create a chroropleth map of the US states, using addPolygons, is it possible to have an event which would select the chosen state so that county map data / and a resultant map of that state alone can be produced?

[jcheng5]

Yes, if the map outputId is "foo" you could look at input$foo_shape_click which will give you either NULL or a list like this:

list(
  lat = latitude,
  lng = longitude,
  id = layerId
)

[pssguy]

Thanks Joe. I can extract a lat and lon this way.

However, I want to return the country clicked on, which is, say, in the data$country field from the underlying data object. I assume I can use the data argument of addPolygons but I cannot seem to return it correctly

getMapData = function(data,location,session){
# want to return country
  })

map <-    leaflet(data = data) %>%
addTiles()

 map %>% 
addPolygons(...,
 data = getMapData(map))

Any help appreciated

[blmoore]

Use layerId (e.g. set polygon layerId's to respective county), then capture as shown above?

[pssguy]

Thanks guys. layerId = data$country looks good

[jcheng5]

Yep. You don't need to pass the data arg to addPolygons, as the
leaflet(data) argument is inherited by default. And you can do layerId = ~country instead of data$country, if you want to. Read this whole page for
more information: http://rstudio.github.io/leaflet/map_widget.html

On Fri, Jun 5, 2015 at 6:57 AM pssguy notifications@github.com wrote:

Thanks guys. layerId = data$country looks good

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#41 (comment).

[efh0888]

Hey Joe,

This was super helpful.

I've been able to implement a drill-down leaflet map going from country to state/province with an info control that changes on hover, but it's still pretty buggy. Would you mind looking at my code at https://github.com/efh0888/leafletDrilldown for some help? The README has all the details...

Edit: you can also see a live version at https://efh0888.shinyapps.io/leafletDrilldown