dpseidel/tidyjson

Tidy your JSON data in R with tidyjson

tidyjson

tidyjson provides tools for turning complex json into tidy data.

Installation

Get the released version from CRAN:

install.packages("tidyjson")

or the development version from github:

devtools::install_github("jeremystan/tidyjson")

Examples

The following example takes a character vector of 500 documents in the worldbank dataset and spreads out all objects. Every JSON object key gets its own column with types inferred, so long as the key does not represent an array. When recursive=TRUE (the default behavior), spread_all does this recursively for nested objects and creates column names using the sep parameter (i.e. {"a":{"b":1}} with sep='.' would generate a single column: a.b).

library(dplyr)
library(tidyjson)

worldbank %>% spread_all
#> # A tbl_json: 500 x 8 tibble with a "JSON" attribute
#>           `attr(., "JSON")` document.id    boardapprovaldate
#>                       <chr>       <int>                <chr>
#>  1 "{\"_id\":{\"$oid\":..."           1 2013-11-12T00:00:00Z
#>  2 "{\"_id\":{\"$oid\":..."           2 2013-11-04T00:00:00Z
#>  3 "{\"_id\":{\"$oid\":..."           3 2013-11-01T00:00:00Z
#>  4 "{\"_id\":{\"$oid\":..."           4 2013-10-31T00:00:00Z
#>  5 "{\"_id\":{\"$oid\":..."           5 2013-10-31T00:00:00Z
#>  6 "{\"_id\":{\"$oid\":..."           6 2013-10-31T00:00:00Z
#>  7 "{\"_id\":{\"$oid\":..."           7 2013-10-29T00:00:00Z
#>  8 "{\"_id\":{\"$oid\":..."           8 2013-10-29T00:00:00Z
#>  9 "{\"_id\":{\"$oid\":..."           9 2013-10-29T00:00:00Z
#> 10 "{\"_id\":{\"$oid\":..."          10 2013-10-29T00:00:00Z
#> # ... with 490 more rows, and 6 more variables: closingdate <chr>,
#> #   countryshortname <chr>, project_name <chr>, regionname <chr>,
#> #   totalamt <dbl>, `_id.$oid` <chr>

Some objects in worldbank are arrays, which are not handled by spread_all. This example shows how to quickly summarize the top level structure of a JSON collection

worldbank %>% gather_object %>% json_types %>% count(name, type)
#> # A tibble: 8 x 3
#>                  name   type     n
#>                 <chr> <fctr> <int>
#> 1   boardapprovaldate string   500
#> 2         closingdate string   370
#> 3    countryshortname string   500
#> 4                 _id object   500
#> 5 majorsector_percent  array   500
#> 6        project_name string   500
#> 7          regionname string   500
#> 8            totalamt number   500

In order to capture the data in the majorsector_percent array, we can use enter_object to enter into that object, gather_array to stack the array and spread_all to capture the object items under the array.

worldbank %>%
  enter_object(majorsector_percent) %>%
  gather_array %>%
  spread_all %>%
  select(-document.id, -array.index)
#> # A tbl_json: 1,405 x 2 tibble with a "JSON" attribute
#>          `attr(., "JSON")`                                    Name Percent
#>                      <chr>                                   <chr>   <dbl>
#>  1 "{\"Name\":\"Educat..."                               Education      46
#>  2 "{\"Name\":\"Educat..."                               Education      26
#>  3 "{\"Name\":\"Public..." Public Administration, Law, and Justice      16
#>  4 "{\"Name\":\"Educat..."                               Education      12
#>  5 "{\"Name\":\"Public..." Public Administration, Law, and Justice      70
#>  6 "{\"Name\":\"Public..." Public Administration, Law, and Justice      30
#>  7 "{\"Name\":\"Transp..."                          Transportation     100
#>  8 "{\"Name\":\"Health..."        Health and other social services     100
#>  9 "{\"Name\":\"Indust..."                      Industry and trade      50
#> 10 "{\"Name\":\"Indust..."                      Industry and trade      40
#> # ... with 1,395 more rows

API

Spreading objects into columns

• spread_all() for spreading all object values into new columns, with nested objects having concatenated names

• spread_values() for specifying a subset of object values to spread into new columns using the json_chr(), json_dbl() and json_lgl() functions. It is possible to specify multiple parameters to extract data from nested objects (i.e. json_chr('a','b')).

Object navigation

• enter_object() for entering into an object by name, discarding all other JSON (and rows without the corresponding object name) and allowing further operations on the object value

• gather_object() for stacking all object name-value pairs by name, expanding the rows of the tbl_json object accordingly

Array navigation

• gather_array() for stacking all array values by index, expanding the rows of the tbl_json object accordingly

JSON inspection

• json_types() for identifying JSON data types

• json_length() for computing the length of JSON data (can be larger than 1 for objects and arrays)

• json_complexity() for computing the length of the unnested JSON, i.e., how many terminal leaves there are in a complex JSON structure

• is_json family of functions for testing the type of JSON data

JSON summarization

• json_structure() for creating a single fixed column data.frame that recursively structures arbitrary JSON data

• json_schema() for representing the schema of complex JSON, unioned across disparate JSON documents, and collapsing arrays to their most complex type representation

Creating tbl_json objects

• as.tbl_json() for converting a string or character vector into a tbl_json object, or for converting a data.frame with a JSON column using the json.column argument

• tbl_json() for combining a data.frame and associated list derived from JSON data into a tbl_json object

• read_json() for reading JSON data from a file

Converting tbl_json objects

• as.character.tbl_json for converting the JSON attribute of a tbl_json object back into a JSON character string

Included JSON data

• commits: commit data for the dplyr repo from github API

• issues: issue data for the dplyr repo from github API

• worldbank: world bank funded projects from jsonstudio

• companies: startup company data from jsonstudio

Philosophy

The goal is to turn complex JSON data, which is often represented as nested lists, into tidy data frames that can be more easily manipulated.

• Work on a single JSON document, or on a collection of related documents

• Create pipelines with %>%, producing code that can be read from left to right

• Guarantee the structure of the data produced, even if the input JSON structure changes (with the exception of spread_all)

• Work with arbitrarily nested arrays or objects

• Handle 'ragged' arrays and / or objects (varying lengths by document)

• Allow for extraction of data in values or object names

• Ensure edge cases are handled correctly (especially empty data)

• Integrate seamlessly with dplyr, allowing tbl_json objects to pipe in and out of dplyr verbs where reasonable

Related Work

Tidyjson depends upon

• magrritr for the %>% pipe operator
• jsonlite for converting JSON strings into nested lists
• purrr for list operators
• tidyr for unnesting and spreading

Further, there are other R packages that can be used to better understand JSON data

• listviewer for viewing JSON data interactively