Leaflet (R) addPopups: coordinates/properties

Question

I'm fairly new to handling spatial data and leaflet in general. I'm having difficulty creating a popup for my map. Basically what I want in the popup is the coordinates of my polygon and one of the properties (the type of class). Below is an test example of my geoJSON file:

{
  "type": "FeatureCollection",
  "features": [
    {
      "type": "Feature",
      "properties": {"class": "blah"},
      "geometry": {
        "type": "Polygon",
        "coordinates": [
          [
            [
              -81.7987060546875,
              32.74570253945518
            ],
            [
              -81.6229248046875,
              32.16631295696736
            ],
            [
              -80.958251953125,
              32.4263401615464
            ],
            [
              -81.2713623046875,
              32.791892438123696
            ],
            [
              -81.7437744140625,
              32.97180377635759
            ],
            [
              -81.7987060546875,
              32.74570253945518
            ]
          ]
        ]
      }
    },
    {
      "type": "Feature",
      "properties": {"class": "blah2"},
      "geometry": {
        "type": "Polygon",
        "coordinates": [
          [
            [
              -82.056884765625,
              33.55512901742288
            ],
            [
              -81.4471435546875,
              33.247875947924385
            ],
            [
              -81.40869140625,
              33.80653802509606
            ],
            [
              -82.078857421875,
              33.88865750124075
            ],
            [
              -82.40295410156249,
              33.58716733904656
            ],
            [
              -82.056884765625,
              33.55512901742288
            ]
          ]
        ]
      }
    },
    {
      "type": "Feature",
      "properties": {"class": "blahh3"},
      "geometry": {
        "type": "Polygon",
        "coordinates": [
          [
            [
              -83.485107421875,
              32.930318199070534
            ],
            [
              -83.07861328125,
              31.863562548378965
            ],
            [
              -82.21618652343749,
              32.11049589629439
            ],
            [
              -82.97973632812499,
              33.22030778968541
            ],
            [
              -83.726806640625,
              33.211116472416855
            ],
            [
              -83.485107421875,
              32.930318199070534
            ]
          ]
        ]
      }
    }
  ]
}

Here is the code I have so far to create my map, but I'm struggling/don't even know where to start on creating a popup that includes my coordinates and property:

blahTest <- geojson_read("/file/path/...", what = "sp")
fpal <- colorFactor("viridis", blahTest$class)
leaflet(blahTest) %>%
  addTiles() %>%
  addPolygons(stroke = FALSE, smoothFactor = 0.3, fillOpacity = 1,
              color = ~fpal(class)) %>%
  addLegend(colors = ~fpal, opacity = 1.0, labels = ~fpal) %>%
  addPopups()

Thanks in advance!

Answer 1

Overview

Using @patL's suggestion, I used the popup parameter within leaflet::addPolygon() function to add label both the class and coordinates that define each polygon within blahTest.

I saved your sample data as .gejson file and imported it using sf::read_sf() and produced the HTML table within the popup using the htmlTable package after reading How to add an html table to leaflet popup.

# load necessary package
library( htmlTable )
library( leaflet )
library( sf )

# load necessary data 
blahTest <- 
  read_sf(
    dsn = "test.geojson"
    , layer = "OGRGeoJSON"
  )

# map data values to colors
fpal <- colorFactor( palette = "viridis", domain = blahTest$class)

# create map
my.map <-
  leaflet( data = blahTest ) %>%
  addTiles() %>%
  addPolygons( stroke = FALSE
               , smoothFactor = 0.3
               , fillOpacity = 1
               , color = ~fpal( class )
               , popup = paste0(
                 "<b>Class: </b>"
                 , blahTest$class
                 , "<br>"
                 , "<b>Coordinates: </b>"
                 , "<br>"
                 , lapply( 
                     X = blahTest$geometry
                     , FUN = function( i ) 
                       htmlTable( 
                         x = i[[1]]
                         , header = c( "Longitude", "Latitude" )
                       )
                     )
                   ) ) %>%
  addLegend( pal = fpal
             , values = ~class
             , labels = ~class
             , title = "Legend"
             , position = "topright"
             , opacity = 1.0 )
# view map
my.map

# end of script #