If I'm using the automatically generated fillcolor how do I add this pallet to the legend?

[vkentner]

I've looked everywhere for this answer and can't figure out a way to call the automatically generated color pallet in addGlPolygons fillcolor. I know I can define my own color pallet but what if I want to use the automatically generated color pallet with a legend?

  library(mapview)
  library(leaflet)
  library(leafgl)
  library(sf)
     
  fran = st_cast(franconia, "POLYGON")
  #> Warning in st_cast.sf(franconia, "POLYGON"): repeating attributes for all
  #> sub-geometries for which they may not be constant
  
  leaflet() %>%
    addProviderTiles(provider = providers$CartoDB.DarkMatter) %>%
    addGlPolygons(data = fran, fillColor ="SHAPE_AREA", popup = "NAME_ASCI") %>%
    setView(lng = 10.5, lat = 49.5, zoom = 8)%>%
    addLegend(colors="SHAPE_AREA", labels="SHAPE_AREA") #this is the issue

[tim-salabim]

@trafficonese any ideas? You created all the color utils IIRC

[trafficonese]

Hm one option would be to get the RGB colors with makeColorMatrix and convert them to Hex-values.

library(mapview)
library(leaflet)
library(leafgl)
library(sf)

fran = st_cast(franconia, "POLYGON")
fran$color <- sample(1:5, nrow(fran), replace = T)
colname <- "color"
# colname <- "district"
# colname <- "SHAPE_AREA"

fran <- fran[order(fran[[colname]], decreasing = T),]
colrgb <- leafgl::makeColorMatrix(x = colname, data = fran) * 255
cols <- apply(colrgb, 1, function(x)
  rgb(x[1], x[2], x[3], maxColorValue=255))

leaflet() %>%
  addProviderTiles(provider = providers$CartoDB.DarkMatter) %>%
  addGlPolygons(data = fran, fillColor = colname, popup = colname) %>%
  setView(lng = 10.5, lat = 49.5, zoom = 8) %>%
  addLegend(labels=unique(fran[[colname]]), opacity = 1,
            colors=unique(cols))

Another and simpler way would be to include a legend option in the add*-functions that will automatically create the legend for the user. For numeric columns, I would still recommend using a custom palette as each unique value gets its own color and the legend will be quite long and unreadable.

What do you think?

[vkentner]

This is a great solution, Thanks for the help. For my use case I need to use a numeric color pallet so I ended up just defining a custom pallet which I call in the legend. This is an amazingly useful package and I appreciate all your hard work on it!