Leaflet: Labels from the SpatialPolygonsDataFrame

Created on 23 Feb 2017 · 6Comments · Source: rstudio/leaflet

I'm attempting to label polygons based on information within the spatial dataframe. Leveraging an example for points (the last example here) I've attempted the following:

leaflet(mapview::gadmCHE) %>% addPolygons(fillOpacity = 0.5, fillColor = "white", weight = 1,
                                          label = mapply(function(x, y) {
                                            HTML(sprintf("<em>%s:</em>%s", htmlEscape(x), htmlEscape(y)))},
                                            mapview::gadmCHE$NAME_0, mapview::gadmCHE$NAME_1, SIMPLIFY = F),
                                          labelOptions = lapply(1:nrow(houses), function(x) {
                                            labelOptions(direction='auto')
                                          })

I only see a horizontal line. My goal is to slightly "prettify" the labels for some polygons.

Source

okjed

Most helpful comment

@jakeander You will have to determine the coordinates for a proper point within each polygon and use addLabelOnlyMarkers. This is necessary as leaflet has no way of knowing where to put a static label in case of a polygon.
You can use GISTools::poly.labels or rgeos::polygonLabel functions to get optimal points, and then pass them to addLabelOnlyMarkers.

bhaskarvk on 2 Mar 2017

👍2

All 6 comments

I'm not sure why that doesn't work, but this does:

library(htmltools)

leaflet(mapview::gadmCHE) %>%
  addPolygons(fillOpacity = 0.5, fillColor = "white", weight = 1,
    label = ~sprintf("<em>%s:</em> %s", htmlEscape(NAME_0), htmlEscape(NAME_1)) %>% lapply(HTML),
    labelOptions = labelOptions(direction='auto')
  )

It's really annoying that HTML() collapses the string vector, we really need pHTML() or something that marks each individual element as HTML...

jcheng5 on 23 Feb 2017

On a side note, you don't need to supply a list for labelOptions unless you want to apply a different labelOption for each marker/shape.

bhaskarvk on 23 Feb 2017

Thank you both - I discovered after posting that there was something odd specifically with the mapply of the HTML() on that particular dataset (and the one I'm working with) and almost deleted this issue.

okjed on 23 Feb 2017

Is there a way to add static labels to addPolygons? I want the labels to already be on the map and not just appear when I hover over. The noHide attribute doesn't seem to work.