How can I plot individual data points in a map using R/ leaflet?

Question

I am trying to show the individual points in a given place, like a map equivalent of dot plot. I tried with leaflet library in R, but I am only able to map the size of the marker to the continuous variable. Is it possible to map the individual data points as clusters instead of mapping the size of the marker to the continuous variable?

My data looks like this

Lat,Lon,Place,People
19.877263,75.3390241,Aurangabad,1
20.2602939,85.8394548,Bhubaneshwar,2
30.7194022,76.7646552,Chandigarh,23
13.0801721,80.2838331,Chennai,25
11.0018115,76.9628425,Coimbatore,2
27.4844597,94.9019447,Dibrugarh,1
16.2915189,80.4541588,Guntur,1
17.3887859,78.4610647,Hyderabad,4
22.5677459,88.3476023,Kolkata,7
15.8309251,78.0425373,Kurnool,1
9.9256493,78.1228866,Madurai,1

Fever

What do you mean by cluster? Can you show what is your expected output? – Gram

Answer 1

You can use the following code to have dot plot

leaflet(df) %>% addTiles() %>%
  addCircleMarkers(lng = ~Lon, lat = ~Lat, 
             popup = ~Place)

Data

df = structure(list(Lat = c(19.877263, 20.2602939, 30.7194022, 13.0801721, 
11.0018115, 27.4844597, 16.2915189, 17.3887859, 22.5677459, 15.8309251, 
9.9256493), Lon = c(75.3390241, 85.8394548, 76.7646552, 80.2838331, 
76.9628425, 94.9019447, 80.4541588, 78.4610647, 88.3476023, 78.0425373, 
78.1228866), Place = structure(1:11, .Label = c("Aurangabad", 
"Bhubaneshwar", "Chandigarh", "Chennai", "Coimbatore", "Dibrugarh", 
"Guntur", "Hyderabad", "Kolkata", "Kurnool", "Madurai"), class = "factor"), 
    People = c(1L, 2L, 23L, 25L, 2L, 1L, 1L, 4L, 7L, 1L, 1L)), class = "data.frame", row.names = c(NA, 
-11L))

Gram

I did this..then mapped radius of the circle marker to the people..what I am trying is to replace the marker at say, Chennai, with 25 small dots.. is it possible? couldn't find it in the documentation. – Fever

Answer 2

leaflet works great with sf package. Taking a sample of your data points

lat <- c(19.877263, 20.2602939)
lon <- c(75.3390241, 85.8394548)
place <- c("Aurangabad", "Bhubaneshwar")

You can convert them in spatial object using sf package. For leaflet to give you tiles, you need to have WSG84 coordinates. I assumed your data were in this coordinate system.

library(sf)

df <- data.frame(lon, lat, place, stringsAsFactors = FALSE)
points <- st_as_sf(df, coords = c("lon", "lat"), crs = 4326)

Then it's easy to plot with leaflet. Assuming you want markers that popup the name of the place when you click

library(leaflet)
leaflet(df) %>% addTiles() %>% addMarkers(popup = ~ place)

Donella