How to extract the longitude and latitude information from a list

[YuJiang]

Hello everyone. I need your help to extract the longitude and latitude information from a list. I have a bunch of specific addresses and I use this website to get the latitude and longitude for each address, Census Geocoder. Here is my code:

fetch_geocodes <- function(address) {
  # Specify the API endpoint
  base_url <- "https://geocoding.geo.census.gov/geocoder/geographies/onelineaddress"
  
  # Specify the parameters to pass to the API
  params <- list(
    address = address,
    benchmark = "Public_AR_Current",  
    vintage = "Current_Current",
    format = "json"
  )
  
  # Send a GET request to the API
  response <- GET(url = base_url, query = params)
  
  # Check if the request was successful
  if (status_code(response) == 200) {
    # Parse the response to JSON
    data <- content(response, "parsed")
    
    # Print the entire JSON response
    print(data)
    
    # Extract the longitude and latitude
    longitude <- data$result$addressMatches$coordinates$x
    latitude <- data$result$addressMatches$coordinates$y
    
    return(c(longitude, latitude))
  } else {
    stop("Request failed with status ", status_code(response))
  }
}

addresses <- c("Riverside Dr, Apple Valley, CA, 92307",
               "11 Wall Street, New York, NY 10005")
geocodes <- lapply(addresses, fetch_geocodes)

Here is my partial output because the entire one is quite long:

$result
$result$input
$result$input$address
$result$input$address$address
[1] "Riverside Dr, Apple Valley, CA, 92307"


$result$input$vintage
$result$input$vintage$isDefault
[1] TRUE

$result$input$vintage$id
[1] "4"

$result$input$vintage$vintageName
[1] "Current_Current"

$result$input$vintage$vintageDescription
[1] "Current Vintage - Current Benchmark"


$result$input$benchmark
$result$input$benchmark$isDefault
[1] TRUE

$result$input$benchmark$benchmarkDescription
[1] "Public Address Ranges - Current Benchmark"

$result$input$benchmark$id
[1] "4"

$result$input$benchmark$benchmarkName
[1] "Public_AR_Current"



$result$addressMatches
list()

$result
$result$input
$result$input$address
$result$input$address$address
[1] "11 Wall Street, New York, NY 10005"

$result$addressMatches[[1]]$coordinates
$result$addressMatches[[1]]$coordinates$x
[1] -74.01073

$result$addressMatches[[1]]$coordinates$y
[1] 40.70714

For the first address, Riverside Dr, Apple Valley, CA, 92307, it does not extract longitude and latitude from the website, I need to assgin NA to the columns, 'longitude' and 'latitude'. For the second address, $result$addressMatches[[1]]$coordinates provides the longitude and latitude information. However, I don't know how to extract corresponding information from geocodes because it returns NULL.

print(geocodes)
[[1]]
NULL

[[2]]
NULL

I don't understand how to do with it. Really appreciate your help. My target is to get a data frame with three columns, the first one is full_address, the second one is longitude and the third one is latitude.

[scottyd22]

Below is one approach that arrives at the desired outcome. I made a couple slight modifications to your fetch_geocodes() function. First, I assume longitude and latitude are NA. Then, I check to see if anything exists in data$result$addressMatches. If the length is not equal to 0 (i.e. something exists), I take the x and y coordinates. Otherwise, they just remain NA. Finally, I return a data frame with the desired contents.

library(httr)
library(dplyr)

fetch_geocodes <- function(address) {
  # Specify the API endpoint
  base_url <- "https://geocoding.geo.census.gov/geocoder/geographies/onelineaddress"
  
  # Specify the parameters to pass to the API
  params <- list(
    address = address,
    benchmark = "Public_AR_Current",  
    vintage = "Current_Current",
    format = "json"
  )
  
  # Send a GET request to the API
  response <- GET(url = base_url, query = params)
  
  # Check if the request was successful
  if (status_code(response) == 200) {
    # Parse the response to JSON
    data <- content(response, "parsed")
    
    # # Print the entire JSON response
    # print(data)
    
    # Extract the longitude and latitude
    longitude = NA
    if(length(data$result$addressMatches) != 0) {longitude = data$result$addressMatches[[1]]$coordinates$x}
    latitude = NA
    if(length(data$result$addressMatches) != 0) {latitude = data$result$addressMatches[[1]]$coordinates$y}
    
    return(data.frame(full_adress = address, 
                      longitude = longitude, 
                      latitude = latitude))
  } else {
    stop("Request failed with status ", status_code(response))
  }
}

addresses <- c("Riverside Dr, Apple Valley, CA, 92307",
               "11 Wall Street, New York, NY 10005")

geocodes <- lapply(addresses, fetch_geocodes) |> bind_rows()

geocodes
#>                             full_adress longitude latitude
#> 1 Riverside Dr, Apple Valley, CA, 92307        NA       NA
#> 2    11 Wall Street, New York, NY 10005 -74.01073 40.70714

Created on 2023-07-16 with reprex v2.0.2

[YuJiang]

Thanks for your help. Really appreciate it.

[Ajackson]

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