This post explains how to build a
bubble map with R and the
leaflet
package. It shows a set of earthquakes and
their intensity in the Pacific Ocean.
leaflet
is a R package allowing to build interactive maps.
This post follows the
leaflet introduction
and explain how to build a bubble map.
The input required to build such a map is a list of GPS coordinates, with a numeric value attributed to each location to control the bubble size and color.
Markers are added using the addCircleMarkers()
function,
and bubble color is mapped to a color scale build with binning.
# Library
library(leaflet)
# load example data (Fiji Earthquakes) + keep only 100 first lines
data(quakes)
quakes <- head(quakes, 100)
# Create a color palette with handmade bins.
mybins <- seq(4, 6.5, by=0.5)
mypalette <- colorBin( palette="YlOrBr", domain=quakes$mag, na.color="transparent", bins=mybins)
# Prepare the text for the tooltip:
mytext <- paste(
"Depth: ", quakes$depth, "<br/>",
"Stations: ", quakes$stations, "<br/>",
"Magnitude: ", quakes$mag, sep="") %>%
lapply(htmltools::HTML)
# Final Map
m <- leaflet(quakes) %>%
addTiles() %>%
setView( lat=-27, lng=170 , zoom=4) %>%
addProviderTiles("Esri.WorldImagery") %>%
addCircleMarkers(~long, ~lat,
fillColor = ~mypalette(mag), fillOpacity = 0.7, color="white", radius=8, stroke=FALSE,
label = mytext,
labelOptions = labelOptions( style = list("font-weight" = "normal", padding = "3px 8px"), textsize = "13px", direction = "auto")
) %>%
addLegend( pal=mypalette, values=~mag, opacity=0.9, title = "Magnitude", position = "bottomright" )
m
# save the widget in a html file if needed.
# library(htmlwidgets)
# saveWidget(m, file=paste0( getwd(), "/HtmlWidget/bubblemapQuakes.html"))