choropleth ggplot code

ggplot2.r

library(ggplot2)

#extract reference data
mapcounties <- map_data("county")
mapstates <- map_data("state")

#merge data with ggplot county coordinates
mapcounties$county <- with(mapcounties , paste(region, subregion, sep = ","))
mergedata <- merge(mapcounties, unemp_data, by.x = "county", by.y = "counties")
mergedata <- mergedata[order(mergedata$order),]

#draw map
map <- ggplot(mergedata, aes(long,lat,group=group)) + geom_polygon(aes(fill=colorBuckets))
map <- map  + scale_fill_brewer(palette="PuRd") + coord_map(project="globular") + opts(legend.position = "none")

#add state borders
map  <- map  + geom_path(data = mapstates, colour = "white", size = .75)

#add county borders
map  <- map  + geom_path(data = mapcounties, colour = "white", size = .5, alpha = .1)
map