---

Cool interactive maps can be created using the leaflet package. It is pretty straightforward:

library(leaflet)
library(dplyr)

citibike <- readRDS('data/201508.rds')
  
## summarize data to plot  
station.info <- citibike %>%
  group_by(start.station.id) %>%
  summarise(lat=as.numeric(start.station.latitude[1]),
            long=as.numeric(start.station.longitude[1]),
            name=start.station.name[1],
            n.trips=n())


## make plot with station locations 
leaflet(station.info) %>% 
  addTiles() %>%
  addCircles(lng = ~long, lat = ~lat)

When you plot this in Rstudio you can zoom in and out of the plot (too see what it looks like click on the map above). At a later module we will look at how to intergrate interactive maps into web-pages and html presentations.

You often want to add information to the markers in the maps. Again easy:

station.info <- citibike %>%
  group_by(start.station.id) %>%
  summarise(lat=as.numeric(start.station.latitude[1]),
            long=as.numeric(start.station.longitude[1]),
            n.trips=n(),
            name=paste0(start.station.name[1],'<br/>','Number of Trips: ',n.trips))


leaflet(station.info) %>%                              
  addTiles() %>%
  addCircles(lng = ~long, lat = ~lat, popup = ~name)

You can add further information and use an html break where you want line breaks:

station.info <- citibike %>%
  group_by(start.station.id) %>%
  summarise(lat=as.numeric(start.station.latitude[1]),
            long=as.numeric(start.station.longitude[1]),
            n.trips.subscriber=sum(usertype=='Subscriber'),
            n.trips.customer=sum(usertype=='Customer'),
            n.trips = n(),
            name=paste0(start.station.name[1],'<br/>',
                        'Number of Customer Trips: ',n.trips.customer,'<br/>',
                        'Number of Subscriber Trips: ',n.trips.subscriber))

leaflet(station.info) %>% 
  addTiles() %>%
  addCircles(lng = ~long, lat = ~lat, popup = ~name)

Here is a version with less clutter and circle size conveying information (here number of trips):

leaflet(station.info) %>% 
  addTiles() %>%
  addCircles(lng = ~long, 
             lat = ~lat, 
             weight = 1,
             radius = ~sqrt(n.trips)*2,
             popup = ~name) %>%
  addProviderTiles("CartoDB.Positron")