Introduction to JSON
A walk through Twitter using R
and
Basics of ReST API access using R

By: Kevin J. Smith
Kansas City R-Users Group

Introduction

Kevin J. Smith IBM Informix Automation Engineer

Twitter API

JSON

ReST

R httr and jsonlite

Twitter APIs

Twitter ReST APIs: https://dev.twitter.com/rest/public

Step 1: Sign up for an API account https://dev.twitter.com

Create an app for Oauth authentication handles https://dev.twitter.com/apps

Oauth: https://dev.twitter.com/oauth

Why JSON

http://www.json.org/

JSON is most compared to XML

JSON is leaner and fasterSmaller in size. A XML document with the same data is larger than corresponding JSON document

Writing and parsing json by humans and machines is faster

JSON is becoming the defacto object data storage medium replacing XML.

JSON, in the database world, allows for unstructured data to be stored and accessed ex photo metadata

JSON (JavaScript Object Notation)

Key:Value pairsKey any valid unicode string. Special characters like double quotes must be escaped.

Value Number, String, Boolean, Array, Object, null

Example Name:Kevin

Objects or DocumentsKey:Value pairs enclosed in curly brackets

Example {Name:Kevin}

CollectionAn array of documents

Example [ { name:Kevin} ,
{ name : Sheryl} ,
{huh?:what something different}]

JSON Data Types

Value TypesDescription

Numberdouble- precision floating-point format ie 12.138

StringSingle or Double quoted unicode with escaped special characters ie Hello \Kevin\ World

BooleanTrue or false

ArraySquare bracketed list of value types

ObjectCurly bracketed list of key:value types

nullempty

JSON Document example:
{ name : kevin, age : 36.06 , titles : [ Dr. , Sir., Mr., 8284, true ] , offspring_oldest : { name : son, age : 12.21}, offspring_all : [ { name : son, age : 12.21}, { name : daughter , age : 8.92} ] , greying? : false, status : null}

ReST (Representational State Transfer)

HTTP vs ReST vs SOAP

Access Methods: GET, POST, PUT, DELETE, OPTIONS, HEAD, TRACE, CONNECT and PATCH

Headers describes the interaction between the client and the server

Body describes the data interchanged between the client and server

Special data can be sent in the url as query parameters: ie ?key:value&key:value and must be url encoded

R httr

Oauth comes with the httr package. This allows for Oauth tokens and secrets to be used for authenticating a user to a data source

ReST requestGET(), POST(), PUT(),...

JSON replyHeaders(),cookies(), http_status(), content()

cat(json1)[{"created_at":["Fri Jul 08 19:35:07 +0000 2016"],"id":[7.51499876924621e+17],"id_str":["751499876924620800"],"text":["Jupiter's moon, Ganymede, has more water than the Pacific. https://t.co/RGgVqACgq2 https://t.co/Fguz7rXpBj"],"truncated":[false],"extended_entities":{"media":[{"id":[7.51499874420548e+17],"id_str":["751499874420547584"],"indices":[[83],[106]],"media_url":["http://pbs.twimg.com/media/Cm3dJ3eWYAAPCYZ.jpg"],"media_url_https":["https://pbs.twimg.com/media/Cm3dJ3eWYAAPCYZ.jpg"],"url":["https://t.co/Fguz7rXpBj"],"display_url":["pic.twitter.com/Fguz7rXpBj"],"expanded_url":["http://twitter.com/ScienceChannel/status/751499876924620800/photo/1"],"type":["photo"],"sizes":{"medium":{"w":[600],"h":[308],"resize":["fit"]},"large":{"w":[600],"h":[308],"resize":["fit"]},"thumb":{"w":[150],"h":[150],"resize":["crop"]},"small":{"w":[600],"h":[308],"resize":["fit"]}}}]},"source":["Hootsuite"],"in_reply_to_status_id":{},"in_reply_to_status_id_str":{},"in_reply_to_user_id":{},"in_reply_to_user_id_str":{},"in_reply_to_screen_name":{},"user":{"id":[16895274],"id_str":["16895274"]},"geo":{},"coordinates":{},"place":{},"contributors":{},"is_quote_status":[false],"retweet_count":[8],"favorite_count":[10],"favorited":[false],"retweeted":[false],"possibly_sensitive":[false],"possibly_sensitive_appealable":[false],"lang":["en"]}]

json2$text[[1]][1] "Jupiter's moon, Ganymede, has more water than the Pacific. https://t.co/RGgVqACgq2 https://t.co/Fguz7rXpBj"

Conclusion

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Questions?