using diamond, triangle and star shapes in R leaflet - r

Question

I have different types of observations and I want to display them on leaflet using different shapes and colors. Is it possible to use diamond, triangle, star and other shapes in leaflet in R?
I have providing dummy data and created circle markers with differnt colors.
library(leaflet)
lat1= 36+runif(n=5,min=-1,max=1)
lon1 =-115+runif(n=5,min=-1,max=1)
lat2= 35+runif(n=5,min=-0.5,max=0.5)
lon2 =-110+runif(n=5,min=-0.5,max=0.5)
lat3= 34+runif(n=5,min=-0.5,max=0.5)
lon3 =-112+runif(n=5,min=-0.5,max=0.5)
data_all=rbind(data.frame(Longitude=lon1,Latitude=lat1,Group=1),
data.frame(Longitude=lon2,Latitude=lat2,Group=2),
data.frame(Longitude=lon3,Latitude=lat3,Group=3))
pal <- colorFactor(c("red","blue","purple"), domain = c(1,2,3))
leaflet(data_all) %>% addTiles() %>%
addCircleMarkers(~Longitude, ~Latitude,popup=~paste0("Group= ",data_all$Group),
radius = 10,
color = ~pal(Group),
stroke = FALSE, fillOpacity = 1
)

Answer 1

Here's a solution using base R plotting symbols. Basically, you create a series of temporary png files with the desired shape which you then use to represent your data according to the group.
library(leaflet)
# this is modified from
# https://github.com/rstudio/leaflet/blob/master/inst/examples/icons.R#L24
pchIcons = function(pch = 1, width = 30, height = 30, bg = "transparent", col = "black", ...) {
n = length(pch)
files = character(n)
# create a sequence of png images
for (i in seq_len(n)) {
f = tempfile(fileext = '.png')
png(f, width = width, height = height, bg = bg)
par(mar = c(0, 0, 0, 0))
plot.new()
points(.5, .5, pch = pch[i], col = col[i], cex = min(width, height) / 8, ...)
dev.off()
files[i] = f
}
files
}
lat1= 36+runif(n=5,min=-1,max=1)
lon1 =-115+runif(n=5,min=-1,max=1)
lat2= 35+runif(n=5,min=-0.5,max=0.5)
lon2 =-110+runif(n=5,min=-0.5,max=0.5)
lat3= 34+runif(n=5,min=-0.5,max=0.5)
lon3 =-112+runif(n=5,min=-0.5,max=0.5)
data_all=rbind(data.frame(Longitude=lon1,Latitude=lat1,Group=1),
data.frame(Longitude=lon2,Latitude=lat2,Group=2),
data.frame(Longitude=lon3,Latitude=lat3,Group=3))
shapes = c(5, 6, 8) # base R plotting symbols (http://www.statmethods.net/advgraphs/parameters.html)
iconFiles = pchIcons(shapes, 40, 40, col = c("red", "blue", "purple"), lwd = 4)
leaflet(data_all) %>% addTiles() %>%
addMarkers(
data = data_all,
icon = ~ icons(
iconUrl = iconFiles[Group],
popupAnchorX = 20, popupAnchorY = 0
),
popup=~paste0("Group= ",data_all$Group)
)
Obviously, you could use other png files in addMarkers.
This solution is based on a rather hidden example from https://github.com/rstudio/leaflet/blob/master/inst/examples/icons.R#L24