Open Notify API

Data from API’s

Gaston Sanchez

About

In these slides we describe an example to get data from an API with R.

Required Packages

The content in these slides depend on the following packages:

library(tidyverse)   # data wrangling and graphics

library(leaflet)     # for working with geospatial vector-data

library(httr)        # for HTTP requests

library(jsonlite)    # for working with JSON data

Open Notify API

Open Notify API http://open-notify.org/

About Open Notify

Open Notify is an open source project to provide a simple programming interface (API) for some of NASA’s data.

This API is developed and maintained by Nathan Bergey.

http://open-notify.org/about

Open Notify API: Current ISS Location

Open Notify API: Current ISS Location

Current ISS Location

URL:

http://api.open-notify.org/iss-now.json


Returned ISS Location 1 data in JSON format:

{"iss_position": {"longitude": "-58.8531", "latitude": "-28.5444"}, "message": "success", "timestamp": 1699732761}


timestamp is the number of seconds since Jan-01-1970 (UTC)

Getting Data: Approach 1

Getting Data in R: Approach 1

A simple approach to get the location of the ISS is to use readLines() to import the data—returned by the URL—in R.

Because the data is in JSON format, we then use from JSON() to convert it into an R list:

iss_loc_url = "http://api.open-notify.org/iss-now.json"

iss_loc_json = readLines(iss_loc_url)

iss_loc_list = fromJSON(iss_loc_json)

A much simpler approach is to overpass readLines():

iss_loc_url = "http://api.open-notify.org/iss-now.json"

iss_loc_list = fromJSON(iss_loc_url)

Getting Data in R: Approach 1 (cont’d)

iss_loc_url = "http://api.open-notify.org/iss-now.json"

iss_loc_json = readLines(iss_loc_url)

iss_loc_list = fromJSON(iss_loc_json)

iss_loc_list
$iss_position
$iss_position$longitude
[1] "-58.8531"

$iss_position$latitude
[1] "-28.5444"


$message
[1] "success"

$timestamp
[1] 1699732761

Map with "leaflet"

View Plot Code 
iss_loc_dat = data.frame(
  lng = as.numeric(iss_loc_list$iss_position$longitude),
  lat = as.numeric(iss_loc_list$iss_position$latitude)
)

leaflet(data = iss_loc_dat) |>
  addTiles() |>
  addCircleMarkers(
    radius = 50,
    stroke = FALSE, 
    fillOpacity = 0.3) |>
  addMarkers() |>
  setView(lng = iss_loc_dat$lng, lat = iss_loc_dat$lat, zoom = 3)

Map with "leaflet", adding icon of ISS

View Plot Code 
# url of ISS icon from Wikimedia Commons (png file)
wikimedia = "https://upload.wikimedia.org/wikipedia/commons/thumb/d/d0/"
iss = "International_Space_Station.svg/"
png = "320px-International_Space_Station.svg.png"
iss_icon = paste0(wikimedia, iss, png)

# define icon properties
issIcon <- makeIcon(
  iconUrl = iss_icon,
  iconWidth = 100,
  iconHeight = 70,
  iconAnchorX = 50,
  iconAnchorY = 35)

# leaflet map
leaflet(data = iss_loc_dat) |>
  addTiles() |>
  addCircleMarkers(
    lng = ~lng, 
    lat = ~lat,
    radius = 70,
    stroke = FALSE, 
    fillOpacity = 0.3) |>
  addMarkers(
    lng = ~lng, 
    lat = ~lat, 
    icon = issIcon) |> 
  setView(lng = iss_loc_dat$lng, lat = iss_loc_dat$lat, zoom = 2)
Error in get(x, envir = ns, inherits = FALSE): object '.b64EncodeFile' not found

Getting Data: Approach 2

Getting Data in R: Approach 2

Another approach to get the location of the ISS is to:

  1. make an HTTP request with GET()

  2. extract the content from the request object

res = GET("http://api.open-notify.org/iss-now.json")
res
Response [https://api.open-notify.org/astros.json]
  Date: 2023-11-11 20:51
  Status: 200
  Content-Type: application/json
  Size: 113 B
names(res)
[1] "url"         "status_code" "headers"     "all_headers" "cookies"    
[6] "content"     "date"        "times"       "request"     "handle"

Getting Data in R: Approach 2 (cont’d)

# res$content is a "raw" vector (i.e. binary data format)
res$content
  [1] 7b 22 69 73 73 5f 70 6f 73 69 74 69 6f 6e 22 3a 20 7b 22 6c
 [21] 61 74 69 74 75 64 65 22 3a 20 22 2d 31 32 2e 36 36 30 38 22
 [41] 2c 20 22 6c 6f 6e 67 69 74 75 64 65 22 3a 20 22 2d 39 2e 35
 [61] 30 37 33 22 7d 2c 20 22 6d 65 73 73 61 67 65 22 3a 20 22 73
 [81] 75 63 63 65 73 73 22 2c 20 22 74 69 6d 65 73 74 61 6d 70 22
[101] 3a 20 31 36 39 39 38 39 34 37 31 32 7d


# convert to character type
rawToChar(res$content)
[1] "{\"iss_position\": {\"latitude\": \"-28.5444\", \"longitude\": \"-58.8531\"}, \"message\": \"success\", \"timestamp\": 1699732761}"

Getting Data in R: Approach 2 (cont’d)

iss_loc_list = fromJSON(rawToChar(res$content))

iss_loc_list
$iss_position
$iss_position$longitude
[1] "-58.8531"

$iss_position$latitude
[1] "-28.5444"


$message
[1] "success"

$timestamp
[1] 1699732761

People in Space

People in Space

URL:

http://api.open-notify.org/astros.json


Returned number of people 1 in JSON format:

{"message": "success", "people": [{"name": "Jasmin Moghbeli", "craft": "ISS"}, {"name": "Andreas Mogensen", "craft": "ISS"}, {"name": "Satoshi Furukawa", "craft": "ISS"}, {"name": "Konstantin Borisov", "craft": "ISS"}, {"name": "Oleg Kononenko", "craft": "ISS"}, {"name": "Nikolai Chub", "craft": "ISS"}, {"name": "Loral O'Hara", "craft": "ISS"}], "number": 7}

Getting Data with GET request

res = GET("http://api.open-notify.org/astros.json")

res
Response [https://api.open-notify.org/astros.json]
  Date: 2023-11-11 20:52
  Status: 200
  Content-Type: application/json
  Size: 360 B

Getting Data with GET request (cont’d)

iss_astros_list = fromJSON(rawToChar(res$content))

iss_astros_list
$message
[1] "success"

$people
                name craft
1    Jasmin Moghbeli   ISS
2   Andreas Mogensen   ISS
3   Satoshi Furukawa   ISS
4 Konstantin Borisov   ISS
5     Oleg Kononenko   ISS
6       Nikolai Chub   ISS
7       Loral O'Hara   ISS

$number
[1] 7

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