ggplot2 mapping county boundries in one color and state boundries in another on the same map
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问题 I am creating a choropleth county map with grey borders, and I also want to include the state boundries in black. Does anyone know how I go about adding a second layer of state mapping to an existing county map? Here's the data set and code I ended up using: #load libraries library(ggplot2) library(ggmap) library(maps) library(plyr) #get wif file wip <- read.csv("wip.csv") #get map data for US counties and states county_map <- map_data("county") state_map <- map_data("state") #merge wip and