A demo of leaflet using a color legend

leafletMapWithLegend.R

#devtools::install_github("rstudio/leaflet", ref="feature/color-legend")
library(leaflet)
library(RColorBrewer)
set.seed(100)
pdf <- data.frame(Latitude = runif(100, -90,90), Longitude = runif(100, -180,180))

#make a property with colors
pdf$Study <- rep(1:10,10)

#need to create a pal using colorbin
pal = colorBin('RdYlBu', as.numeric(pdf$Study), 5)

#the map with a legend
leaflet(pdf) %>% addTiles()  %>%
  addCircleMarkers(lat = ~ Latitude, lng = ~ Longitude, color= pal(pdf$Study)) %>%
  addLegend(pal = pal, values = pdf$Study, title="Study")