Simple Point Maps in R

Mapping Points in R

My goal is a streamlined and self-contained freeware map maker with points denoting addresses. It is a three step process that involves:

  1. Get a map.
  2. Geocode the addresses into latitude and longitude.
  3. Combine the the two with a first map layer and a second layer on top that contains the points.

From there, it is pretty easy to get fancy using ggplotly to put relevant text hovers into place.

Get a map.

There are a few map sources that R can access. Google has now made most features pay to access with generous free allocations. It is worth it to sign up if one plans to use it frequently. I have never actually paid for use but I do not use it much. There are nice instructions in a post by littlemissdata. The other issue is the type of map. The coordinates are crucial and I will need a map that is bounded on latitude and longitude. For that purpose, I think I will use ggmap. The register_google line invokes my Google API key.

pdx_map <- get_map(getbb("portland oregon"), maptype = "roadmap")

Load Some Data and Geocode it with Google

First, to get the data. I will create some data using the Portland Center but it could easily be replaced with imported data.

Portland.Center <- data.frame(address = c("905 NW 12th Ave, Portland, OR 97209"), stringsAsFactors = FALSE)
Portland.Center <- Portland.Center %>% mutate_geocode(., address)
##                               address       lon     lat
## 1 905 NW 12th Ave, Portland, OR 97209 -122.6836 45.5295

Put them together

Because they are same source geocodings, this works directly.

ggmap(pdx_map) + geom_point(data=Portland.Center, aes(x=lon, y=lat), size=3, color="magenta")

Now to Try Without Google

First, an open source map. <- get_stamenmap(getbb("portland oregon"), 
                         zoom = 14)

Free Geocode

Geocoded.PDX <- geocode_OSM(Portland.Center$address, = TRUE) %>% select(query, lat, lon)
p1 <- ggmap( + geom_point(data=Geocoded.PDX, aes(x=lon, y=lat, text=query), size=3, color="magenta")
p1a <- ggplotly(p1)
  widgetframe::frameableWidget(p1a), here:::here('static/img/widgets/smp1map.html'))


A very cool toy is leaflet. The markers work the way as geom_point but hovers can be replaced with popups of various forms. I really like this.

##                                 query      lat       lon
## 1 905 NW 12th Ave, Portland, OR 97209 45.52957 -122.6836
m <- leaflet() %>% addTiles() %>% addMarkers(., data=Geocoded.PDX, lng=~lon, lat=~lat, popup = ~query)
  widgetframe::frameableWidget(m), here:::here('static/img/widgets/mmmap.html'))
Robert W. Walker
Associate Professor of Quantitative Methods

My research interests include causal inference, statistical computation and data visualization.