Area Choropleth - R version of http://bl.ocks.org/mbostock/4206573
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library(rgeos) | |
library(rgdal) # needs gdal > 1.11.0 | |
library(ggplot2) | |
# map theme | |
devtools::source_gist("https://gist.github.com/hrbrmstr/33baa3a79c5cfef0f6df") | |
# topojson from the bl.ocks example | |
map = readOGR("us.json", "counties") | |
# calculate (retrieve) area | |
map_area <- data.frame(id=0:(length(map@data$id)-1), | |
area=sapply(slot(map, "polygons"), slot, "area") ) | |
# state borders | |
states = readOGR("us.json", "states") | |
states_df <- fortify(states) | |
# create map data frame and merge area info | |
map_df <- fortify(map) | |
map_df <- merge(map_df, map_area, by="id") | |
gg <- ggplot() | |
gg <- gg + geom_map(data=map_df, map=map_df, | |
aes(map_id=id, x=long, y=lat, group=group, fill=log1p(area)), | |
color="white", size=0.05) | |
gg <- gg + geom_map(data=states_df, map=states_df, | |
aes(map_id=id, x=long, y=lat, group=group), | |
color="white", size=0.5, alpha=0) | |
gg <- gg + scale_fill_continuous(low="#ccebc5", high="#084081") | |
# US continental extents - not showing alaska & hawaii | |
gg <- gg + xlim(-124.848974, -66.885444) | |
gg <- gg + ylim(24.396308, 49.384358) | |
gg <- gg + coord_map() | |
gg <- gg + labs(x="", y="", title="Area Choropleth") | |
gg <- gg + theme_map() | |
gg <- gg + theme(legend.position="none") | |
ggsave("areachoropleth.svg", gg, width=11, height=6) | |
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