CODEWITHSUNDEEP
jsonr
Parseltongue
Parseltongue

Reputation: 11657

JSON Processing Error in R

I'm trying to reverse geocode a dataframe of lat/long coordinates. For some reason, the code spits out a single FIPS code, and stops with error messages. I'm not sure what is going on -- could it be the server rate-limiting queries?

dput(latlon)

structure(list(lat = c(38.6536995, 28.5959782, 39.2349128, 40.6988037, 
36.7276906, 35.0481824), lon = c(-121.3526261, -81.4514073, -76.6117247, 
-73.9183688, -119.803458, -106.4910219)), .Names = c("lat", "lon"
), row.names = c(NA, -6L), class = "data.frame")

#Reverse-Geocoding Function to get county
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)
  return(as.character(json$County['FIPS']))
}


latlong2fips(latlon$lat, latlon$lon)

[1] "06067"

Warning messages:
1: In if (is.na(encoding)) return(0L) :
  the condition has length > 1 and only the first element will be used
2: In if (is.na(i)) { :
  the condition has length > 1 and only the first element will be used

Upvotes: 1

Views: 88

Answers (1)

SymbolixAU
SymbolixAU

Reputation: 26248

The error is because fromJSON doesn't accept a vector. So you need to apply fromJSON to each element of your vector.

I also use jsonlite as my go-to JSON parser in R. 

latitude <- latlon$lat
longitude <- latlon$lon

url <- "http://data.fcc.gov/api/block/find?format=json&latitude=%f&longitude=%f"
url <- sprintf(url, latitude, longitude)
json <- RCurl::getURL(url)

## up to here gives you a vector of results, so you now need to extract the 'FIPS' for each vector element
lapply(json, function(x){
  jsonlite::fromJSON(x)$County$FIPS
})

$`http://data.fcc.gov/api/block/find?format=json&latitude=38.653700&longitude=-121.352626`
[1] "06067"

$`http://data.fcc.gov/api/block/find?format=json&latitude=28.595978&longitude=-81.451407`
[1] "12095"

$`http://data.fcc.gov/api/block/find?format=json&latitude=39.234913&longitude=-76.611725`
[1] "24510"

$`http://data.fcc.gov/api/block/find?format=json&latitude=40.698804&longitude=-73.918369`
[1] "36047"

$`http://data.fcc.gov/api/block/find?format=json&latitude=36.727691&longitude=-119.803458`
[1] "06019"

$`http://data.fcc.gov/api/block/find?format=json&latitude=35.048182&longitude=-106.491022`
[1] "35001"

Upvotes: 3

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