20 Human geography lab: Annex 5

pacman::p_load(usmap, tidyverse)

20.1 Using `ggplot2` package

usa <- map_data('usa')

Next, we use geom_ploygon function to plot USA map.

ggplot(data=usa, aes(x=long, y=lat, group=group)) + 
  geom_polygon(fill='lightblue') + 
  theme(axis.title.x=element_blank(), axis.text.x=element_blank(), axis.ticks.x=element_blank(),
        axis.title.y=element_blank(), axis.text.y=element_blank(), axis.ticks.y=element_blank()) + 
  ggtitle('U.S.A. Map') + 
  coord_fixed(1.3)

In order to get more information about USA, now we can add state data to the map. Like above, we obtain data from maps and mapdata packages, and use ggplot2 to plot.

state <- map_data("state")

Plot the states with ggplot2

ggplot(data=state, aes(x=long, y=lat, fill=region, group=group)) + 
  geom_polygon(color = "white") + 
  guides(fill=FALSE) + 
  theme(axis.title.x=element_blank(), axis.text.x=element_blank(), axis.ticks.x=element_blank(),
        axis.title.y=element_blank(), axis.text.y=element_blank(), axis.ticks.y=element_blank()) + 
  ggtitle('U.S.A. Map with States') + 
  coord_fixed(1.3)

What if we only care about one state? Definitely, we can draw one state map using ggplot2. Firstly we need to filter data.

washington <- subset(state, region=="washington")
counties <- map_data("county")
washington_county <- subset(counties, region=="washington")

Plot Washington

ca_map <- ggplot(data=washington, mapping=aes(x=long, y=lat, group=group)) + 
  coord_fixed(1.3) + 
  geom_polygon(color="black", fill="gray") + 
  geom_polygon(data=washington_county, fill=NA, color="white") + 
  geom_polygon(color="black", fill=NA) + 
  ggtitle('Washington Map with Counties') + 
  theme(axis.title.x=element_blank(), axis.text.x=element_blank(), axis.ticks.x=element_blank(),
        axis.title.y=element_blank(), axis.text.y=element_blank(), axis.ticks.y=element_blank())
ca_map

20.1 Using ggplot2 package

20.1 Using `ggplot2` package