Setting up the environment

library(leaflet)
## Warning: package 'leaflet' was built under R version 3.5.3

Making the map

Constants are set for the longitude and lattitude of Area 51 and the maximum deviation from the longitude and latitude of the aliens.

lat_51 <- 37.23433
lng_51 <- -115.80666
const <- 1

Then an alien icon is made and put into a list of 20.

alien_icon <- makeIcon(
    iconUrl = 'ET.jpg',
    iconWidth = 31*(215/230),
    iconHeight= 31,
    iconAnchorX = 31 * 215 / 230 / 2,
    iconAnchorY = 16
)
icons <- c(NULL, rep(alien_icon, times=20))

A dataframe of 20 aline locations is randomly generated.

df <- data.frame(
    lat=c(runif(20, min=lat_51-const, max=lat_51+const)),
    lng=c(runif(20, min=lng_51-const, max=lng_51+const))
    )

Finally area 51 is located with the standard marker and the aliens are located with their custom markers.

df %>%
    leaflet() %>%
    addTiles() %>%
    addMarkers(icon=icons, popup="You've found ET") %>%
    addMarkers(lng=lng_51, lat=lat_51, popup="Area 51")