massS <- read.csv("correct_lat_lng_mass_shootings_final_20171116_835.csv", header = T, stringsAsFactors = F)

library(leaflet)
library(yaml)
## Warning: package 'yaml' was built under R version 3.4.3
dat <- massS$Date
loc <- massS$Location
lat <- massS$Lat
long <- massS$Lng

map <- leaflet()

map <- leaflet() %>% addTiles() %>% setView(-93.65, 42.0285, zoom = 3) %>% 
        addMarkers(long, lat, popup = as.character(loc), label = as.character(dat), clusterOptions = markerClusterOptions())
map