I am trying my hands at grabbing data from an API in R.

The API I am using is the Data Science Toolkit's street2coordinates.

Basically this API returns the coordinates for street addresses. I tried using it and it works fine when I pass just one address. Like This:

library(httr)

GET("http://www.datasciencetoolkit.org/street2coordinates/2543+Graystone+Place%2c+Simi+Valley%2c+CA+93065")

I am not sure how to pass multiple addresses to this function.

I tried doing this but the output is something I don't understand. It's a weird list.

addresses <- c("4600 Vegas Dr, Las Vegas, NV 89108","3600 Vegas Dr, Las Vegas, NV 89108")
url <- GET("http://www.datasciencetoolkit.org/street2coordinates/addresses")

library(httr)
library(tidyverse)

base_url <- "http://www.datasciencetoolkit.org/street2coordinates/" 
look_up <- c("4600+Vegas+Dr%2c+Las+Vegas%2c+NV+89108", "3600+Vegas+Dr%2c+Las+Vegas%2c+NV+89108", "2543+Graystone+Place%2c+Simi+Valley%2c+CA+93065")

full_url <- map2_chr(base_url, look_up, paste0)

out <- map(full_url, GET) %>% 
  map_dfr(., ~ {
  content(., as = 'parsed') %>% 
    unlist() %>% 
    enframe() %>% 
      extract(col = name, into =  "key", regex = "([^.]*$)", remove = FALSE)
    })
​

library(httr)
addresses <- c("4600 Vegas Dr, Las Vegas, NV 89108","3600 Vegas Dr, Las Vegas, NV 89108")

for(i in (1:length(addresses))){
  print(GET(paste("http://www.datasciencetoolkit.org/street2coordinates/",addresses)))
}​

Response [http://www.datasciencetoolkit.org/street2coordinates/ 4600 Vegas Dr, Las Vegas, NV 89108]
  Date: 2019-10-26 20:00
  Status: 500
  Content-Type: text/html;charset=utf-8
  Size: 61 B
{
  "error": "Empty string passed in to street2coordinates"
Response [http://www.datasciencetoolkit.org/street2coordinates/ 3600 Vegas Dr, Las Vegas, NV 89108]
  Date: 2019-10-26 20:00
  Status: 500
  Content-Type: text/html;charset=utf-8
  Size: 61 B
{
  "error": "Empty string passed in to street2coordinates"

Querying a Web service API typically involves the following steps:

1. submit the request
2. check for any server error
3. parse the response
4. convert to a data frame

In the following example we will submit a request for police reported crime data from the UK Police API. The API uses both HTTP GET and POST requests and provides content in JSON data format.

The two key R packages for submitting HTTP requests to Web service APIs and parsing the content of the response are httr and jsonlite. Let’s load them into our R session. The tidyverse package is also loaded because it contains a suite of useful functions.

library(tidyverse) ; library(httr) ; library(jsonlite)

Then we’ll parse the JSON content and and convert it to a data frame.

df <- fromJSON(response, flatten = TRUE) %>% 
  data.frame()