ggplot2 map using borders()

ggplot_map.R

# In response to a question on our ggplot2/mapping post 
# (http://zevross.com/blog/2014/07/16/mapping-in-r-using-the-ggplot2-package/)
# this is an example of using ggplot2's built-in
# borders() function and an external shapefile

# The shapefile used in that blog post is a projected shapefile
# but by default the borders() function uses unprojected
# boundaries so you will need to "unproject" the shapefile
# for the borders to match. An alternative would be to assign 
# a projection with map() arguments

# The shapefile is from:
# http://www.nyc.gov/html/dcp/html/bytes/districts_download_metadata.shtml


library(rgdal) 

# this is projected and won't match up
# with ggplot2's default "border" layer
cnty<-readOGR("nybb.shp", layer="nybb")
proj4string(cnty) # see projection

# "unproject" this -- assign unprojected geographic coord system
# wgs84 would be nearly equivalent but we use nad83
cnty<-spTransform(cnty, CRS("+proj=longlat +datum=NAD83"))

# now it matches
library(ggplot2)
library(maps)
data(us.cities)
capitals <- subset(us.cities, capital == 2 & country.etc=="NY")
ggplot(capitals, aes(long, lat)) +
  borders('state', region = c('new york')) +
  geom_point(aes(size = pop)) +
  geom_polygon(data=cnty, aes(long,lat, group=group))

Hi,

Could you tell me how to find "mybb.shp"? When I tried cnty<-readOGR("nybb.shp", layer="nybb"), it returned with error "Error in ogrInfo(dsn = dsn, layer = layer, encoding = encoding, use_iconv = use_iconv, : Cannot open file".

I am trying to get polygon map plots of the five boroughs of NYC separately, Do you know whether there is a way to do that?

Thank you very much!

Best,

Yuying
[email protected]

Hi,

I got it. It turned out that I need to download "nybb.shp" before use it. Thank you very much!!

Best,

Yuying
[email protected]