df <- data.frame(name = c("Mumbai", "New Delhi", "Kolkata", "Chennai"),
  lat = c(19.0760, 28.6139, 22.5726, 13.0827),
                 lng = c(72.8777, 77.2090, 88.3639, 80.2707),
  cases = c(8068, 2918, 649, 1885))
my_map <- df %>%
          leaflet() %>%
                        addTiles() %>%
                    addMarkers(lat = df$lat, lng = df$lng, popup = df$name) %>%
                                                                                addCircles(weight = 1, radius = df$cases*50)
my_map