title: How to customize legend labels in R Leaflet
body: <p>I have a R script for making  a shiny app with leaflet map.
  The map includes a legend based on quartile calculation. The legend shows the range of each quartile, but I would like to make to show like "1st Quartile", "2nd Quartile", and so on. I tried to add "labels" under "AddLegend" but of not use. DO you know how?
  You can see the script and relevant files from the GitHub link below. Thank you so much.</p>
  
  <p><a href="https://github.com/e5t2o/exploring_shiny/blob/master/InteractiveMap/app.R" rel="nofollow noreferrer">https://github.com/e5t2o/exploring_shiny/blob/master/InteractiveMap/app.R</a></p>