Shading counties using FIPS code in R map

Question

I am looking for a way to shade counties on the US maps in R. I have list of numeric/char county FIPS code that I can input as parameter. I just need to highlight these coun

Answer 1

Here's an example using the maps library:

library(maps)
library(dplyr)

data(county.fips)

## Set up fake df_pop_county data frame
df_pop_county <- data.frame(region=county.fips$fips)
df_pop_county$value <- county.fips$fips
y <- df_pop_county$value
df_pop_county$color <- gray(y / max(y))

## merge population data with county.fips to make sure color column is
## ordered correctly.
counties <- county.fips %>% left_join(df_pop_county, by=c('fips'='region'))
map("county", fill=TRUE, col=counties$color)

Here's the resulting map:

Notice that counties with lower FIPS are darker, while counties with higher FIPS are lighter.