Latitude/Longitude to FIPS Codes via the FCC's API

latlong2fips.r

# FCC's Census Block Conversions API
# http://www.fcc.gov/developers/census-block-conversions-api
latlong2fips <- function(latitude, longitude) {
  url <- "http://data.fcc.gov/api/block/find?format=json&latitude=%f&longitude=%f"
  url <- sprintf(url, latitude, longitude)
  json <- RCurl::getURL(url)
  json <- RJSONIO::fromJSON(json)
  as.character(json$County['FIPS'])
}

# Orange County
latlong2fips(latitude=28.35975, longitude=-81.421988)

Thanks for this useful code! Came in very clutch for me.

Here's my edit:

Use Lat/Long to lookup missing county FIPS ------------------------------

if (!require("RJSONIO")) install.packages("RJSONIO")
latlong2fips =
function(latitude, longitude) {
url <- "https://geo.fcc.gov/api/census/area?lat=%s&lon=%s&censusYear=2010&format=json"
url <- sprintf(url, latitude, longitude)
json <- RJSONIO::fromJSON(url)
as.character(json[["results"]][[1]][["county_fips"]])
}
latlong2fips(latitude=28.35975, longitude=-81.421988)
The result:
"12095"

Since it's probably most useful to use this not for a single lookup, but for lots of inputs, here's a short code snippet to help with that (if you have a vectorized way of doing it, please share!)

Make a data.table
a = data.table(latitude=c(28.35975,28.36975,29.33), longitude=c(-81.421988,-81.431988,-81.55))
Pre-allocate space
a[,fips:="0"]

Loop and add the new FIPS codes
for(i in 1:nrow(a)){
lat = a[i, latitude]
lon = a[i, longitude]
a[i, fips := latlong2fips(latitude = lat, longitude = lon)]
}