gather_array {tidyjson}

Gather a JSON array into index-value pairs

Description

gather_array collapses a JSON array into index-value pairs, creating a new column 'array.index' to store the index of the array, and storing values in the 'JSON' attribute for further tidyjson manipulation. All other columns are duplicated as necessary. This allows you to access the values of the array just like gather_object lets you access the values of an object.

Usage

gather_array(.x, column.name = default.column.name)

Arguments

.x

a json string or tbl_json object whose JSON attribute should always be an array

column.name

the name to give to the array index column created

Details

JSON arrays can be simple vectors (fixed or varying length number, string or logical vectors with or without null values). But they also often contain lists of other objects (like a list of purchases for a user). Thus, the best analogy in R for a JSON array is an unnamed list.

gather_array is often preceded by enter_object when the array is nested under a JSON object, and is often followed by gather_object or enter_object if the array values are objects, or by append_values to append all scalar values as a new column or json_types to determine the types of the array elements (JSON does not guarantee they are the same type).

Value

a tbl_json object

See Also

gather_object to gather a JSON object, enter_object to enter into an object, gather to gather name-value pairs in a data frame

Examples

# A simple character array example
json <- '["a", "b", "c"]'

# Check that this is an array
json %>% json_types

# Gather array and check types
json %>% gather_array %>% json_types

# Extract string values
json %>% gather_array %>% append_values_string

# A more complex mixed type example
json <- '["a", 1, true, null, {"name": "value"}]'

# Then we can use the column.name argument to change the name column
json %>% gather_array %>% json_types

# A nested array
json <- '[["a", "b", "c"], ["a", "d"], ["b", "c"]]'

# Extract both levels
json %>% gather_array("index.1") %>% gather_array("index.2") %>%
  append_values_string

# Some JSON begins as an array
commits %>% gather_array

# We can use spread_all to capture all values
# (recursive = FALSE to limit to the top level object)
library(dplyr)
commits %>% gather_array %>% spread_all(recursive = FALSE) %>% glimpse