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JSONLITE
A SIMPLE AND ROBUST JSON PARSER AND GENERATOR FOR R

Package index
Search the jsonlite package

Vignettes
 * Combining pages of JSON data with jsonlite
 * Fetching JSON data from REST APIs
 * Getting started with JSON and jsonlite

Functions
117

Source code
100

Man pages
11
 * base64: Encode/decode base64
 * flatten: Flatten nested data frames
 * fromJSON: Convert R objects to/from JSON
 * gzjson: Gzipped JSON
 * prettify: Prettify or minify a JSON string
 * rbind_pages: Combine pages into a single data frame
 * read_json: Read/write JSON
 * serializeJSON: serialize R objects to JSON
 * stream_in: Streaming JSON input/output
 * unbox: Unbox a vector or data frame
 * validate: Validate JSON
 * Browse all...


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Getting started with JSON and jsonlite
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GETTING STARTED WITH JSON AND JSONLITE
IN JSONLITE: A SIMPLE AND ROBUST JSON PARSER AND GENERATOR FOR R

library(knitr)
opts_chunk$set(comment="")

#this replaces tabs by spaces because latex-verbatim doesn't like tabs
#no longer needed because yajl does not use tabs.
#toJSON <- function(...){
#  gsub("\t", "  ", jsonlite::toJSON(...), fixed=TRUE);
#}



GETTING STARTED WITH JSON AND JSONLITE

The jsonlite package is a JSON parser/generator optimized for the web. Its main
strength is that it implements a bidirectional mapping between JSON data and the
most important R data types. Thereby we can convert between R objects and JSON
without loss of type or information, and without the need for any manual data
munging. This is ideal for interacting with web APIs, or to build pipelines
where data structures seamlessly flow in and out of R using JSON.

library(jsonlite)
all.equal(mtcars, fromJSON(toJSON(mtcars)))


This vignette introduces basic concepts to get started with jsonlite. For a more
detailed outline and motivation of the mapping, see: arXiv:1403.2805.


SIMPLIFICATION

Simplification is the process where JSON arrays automatically get converted from
a list into a more specific R class. The fromJSON function has 3 arguments which
control the simplification process: simplifyVector, simplifyDataFrame and
simplifyMatrix. Each one is enabled by default.

| JSON structure | Example JSON data | Simplifies to R class | Argument in
fromJSON | |
----------------------|----------------------------------------------------------|-----------------------|----------------------|
| Array of primitives | ["Amsterdam", "Rotterdam", "Utrecht", "Den Haag"] |
Atomic Vector | simplifyVector | | Array of objects | [{"name":"Erik",
"age":43}, {"name":"Anna", "age":32}] | Data Frame | simplifyDataFrame | | Array
of arrays | [ [1, 2, 3], [4, 5, 6] ] | Matrix | simplifyMatrix |


ATOMIC VECTORS

When simplifyVector is enabled, JSON arrays containing primitives (strings,
numbers, booleans or null) simplify into an atomic vector:

# A JSON array of primitives
json <- '["Mario", "Peach", null, "Bowser"]'

# Simplifies into an atomic vector
fromJSON(json)


Without simplification, any JSON array turns into a list:

# No simplification:
fromJSON(json, simplifyVector = FALSE)



DATA FRAMES

When simplifyDataFrame is enabled, JSON arrays containing objects (key-value
pairs) simplify into a data frame:

json <-
'[
  {"Name" : "Mario", "Age" : 32, "Occupation" : "Plumber"}, 
  {"Name" : "Peach", "Age" : 21, "Occupation" : "Princess"},
  {},
  {"Name" : "Bowser", "Occupation" : "Koopa"}
]'
mydf <- fromJSON(json)
mydf


The data frame gets converted back into the original JSON structure by toJSON
(whitespace and line breaks are ignorable in JSON).

mydf$Ranking <- c(3, 1, 2, 4)
toJSON(mydf, pretty=TRUE)


Hence you can go back and forth between dataframes and JSON, without any manual
data restructuring.


MATRICES AND ARRAYS

When simplifyMatrix is enabled, JSON arrays containing equal-length sub-arrays
simplify into a matrix (or higher order R array):

json <- '[
  [1, 2, 3, 4],
  [5, 6, 7, 8],
  [9, 10, 11, 12]
]'
mymatrix <- fromJSON(json)
mymatrix


Again, we can use toJSON to convert the matrix or array back into the original
JSON structure:

toJSON(mymatrix, pretty = TRUE)


The simplification works for arrays of arbitrary dimensionality, as long as the
dimensions match (R does not support ragged arrays).

json <- '[
   [[1, 2], 
    [3, 4]],
   [[5, 6], 
    [7, 8]],
   [[9, 10],
    [11, 12]]
]'
myarray <- fromJSON(json)
myarray[1, , ]
myarray[ , ,1]


This is all there is to it! For a more detailed outline and motivation of the
mapping, see: arXiv:1403.2805.






TRY THE JSONLITE PACKAGE IN YOUR BROWSER

library(jsonlite) help(jsonlite)
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jsonlite documentation built on July 9, 2023, 6:11 p.m.

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