Polygon shapefile doesn't render

Question

I'm trying to add some boundaries to a leaflet map using the leaflet package in R. I write:

library(rgdal)
fw<-readOGR("/local/path/to/FWC_UT_MASTER_0623_2016.shp",verbose=FALSE)`

To add the polygons to leaflet, I write:

library(leaflet)
  fw %>%
  leaflet() %>% 
  addTiles() %>%
  addPolygons(stroke = FALSE, fillOpacity = 0.5, smoothFactor = 0.5) 

It seems intuitive enough. I can't for the life of me figure why these little guys wont render. I thought the SpatialPolygonsDataFrame needed to be in WGS84. The original file is not.

..@ proj4string:Formal class 'CRS' [package "sp"] with 1 slot
.. .. ..@ projargs: chr "+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null +no_defs"

So i tried reprojecting the original shapefile

fw.proj<-spTransform(fw, CRS("+init=epsg:4326"))

However,

fw.proj %>%
  leaflet() %>% 
  addTiles() %>%
  addPolygons(stroke = FALSE, fillOpacity = 0.5, smoothFactor = 0.5)

renders a blank map as well. I saved the original shape file here: https://github.com/uky994/firewise

Answer 1

I'm surprised your readOGR didn't issue any warnings, as the layer argument is required.

But you're right that you need to transform the shape into lat/lon as this is what leaflet expects.

Here's some working code; you'll have to figure out the exact CRS you want to use.

library(leaflet)
library(rgdal)

setwd("~/Downloads/firewise-master/")
fw <- readOGR(dsn = ".",
              layer = "FWC_UT_MASTER_0623_2016",
              verbose = FALSE)

fw_latlon <- spTransform(fw, CRS("+proj=longlat +datum=WGS84"))

leaflet() %>%
  addTiles() %>%
  addPolygons(data = fw_latlon)