library(maps)
library(mapdata)
library(ggplot2)

map("state")
map("france")
map("nz")
map("state", fill=T, col=rainbow(10))
map("usa")
map( )

mn.nd.sd <- c("minnesota", "north dakota", "south dakota")
map("state", mn.nd.sd)
map("state", "illinois")

states_map <- map_data("state")
ggplot(states_map, aes(x=long, y=lat, group=group)) +
    geom_polygon(fill="white", colour="black")

world_map <- map_data("world")

east_asia <- map_data("world", region=c("Japan", "China", "North Korea",
   "South Korea"))
ggplot(east_asia, aes(x=long, y=lat, group=group, fill=region)) +
   geom_polygon(colour="black") +
   scale_fill_brewer(palette="Set2")

# plot New Zealand from world map
nz1 <- map_data("world", region="New Zealand")
nz1 <- subset(nz1, long > 0 & lat > -48)  # trim off islands
ggplot(nz1, aes(x=long, y=lat, group=group)) + geom_path( )

# Plot New Zealand from nz map.
nz2 <- map_data("nz")
ggplot(nz2, aes(x=long, y=lat, group=group)) + geom_path( )

# Creating a choropeleth map
crimes <- data.frame(state=tolower(rownames(USArrests)), USArrests)
crimes
states_map <- map_data("state")
crime_map <- merge(states_map, crimes, by.x="region", by.y="state")
head(crime_map)

library(plyr)
crime_map <- arrange(crime_map, group, order)
head(crime_map)

# Need mapproj package for next statements.
ggplot(crime_map, aes(x=long, y=lat, group=group, fill=Assault)) +
   geom_polygon(colour="black") +
   coord_map("polyconic")


ggplot(crime_map, aes(x=long, y=lat, group=group, fill=Assault)) +
   geom_polygon(colour="black") +
   scale_fill_gradient2(low="#559999", mid="gray90", high="#BB650B",
          midpoint=median(crimes$Assault)) +
   expand_limits(x=states_map$long, y=states_map$lat) +
   coord_map("polyconic")