hoist {tidyr}

Hoist values out of list-columns

Description

hoist() allows you to selectively pull components of a list-column into their own top-level columns, using the same syntax as purrr::pluck().

Learn more in vignette("rectangle").

Usage

hoist(
  .data,
  .col,
  ...,
  .remove = TRUE,
  .simplify = TRUE,
  .ptype = NULL,
  .transform = NULL
)

Arguments

.data

A data frame.

.col

<tidy-select> List-column to extract components from.

...

<dynamic-dots> Components of .col to turn into columns in the form col_name = "pluck_specification". You can pluck by name with a character vector, by position with an integer vector, or with a combination of the two with a list. See purrr::pluck() for details.

The column names must be unique in a call to hoist(), although existing columns with the same name will be overwritten. When plucking with a single string you can choose to omit the name, i.e. hoist(df, col, "x") is short-hand for hoist(df, col, x = "x").

.remove

If TRUE, the default, will remove extracted components from .col. This ensures that each value lives only in one place. If all components are removed from .col, then .col will be removed from the result entirely.

.simplify

If TRUE, will attempt to simplify lists of length-1 vectors to an atomic vector. Can also be a named list containing TRUE or FALSE declaring whether or not to attempt to simplify a particular column. If a named list is provided, the default for any unspecified columns is TRUE.

.ptype

Optionally, a named list of prototypes declaring the desired output type of each component. Alternatively, a single empty prototype can be supplied, which will be applied to all components. Use this argument if you want to check that each element has the type you expect when simplifying.

If a ptype has been specified, but simplify = FALSE or simplification isn't possible, then a list-of column will be returned and each element will have type ptype.

.transform

Optionally, a named list of transformation functions applied to each component. Alternatively, a single function can be supplied, which will be applied to all components. Use this argument if you want to transform or parse individual elements as they are extracted.

When both ptype and transform are supplied, the transform is applied before the ptype.

See Also

Other rectangling: unnest_longer(), unnest_wider(), unnest()

Examples

df <- tibble(
  character = c("Toothless", "Dory"),
  metadata = list(
    list(
      species = "dragon",
      color = "black",
      films = c(
        "How to Train Your Dragon",
        "How to Train Your Dragon 2",
        "How to Train Your Dragon: The Hidden World"
      )
    ),
    list(
      species = "blue tang",
      color = "blue",
      films = c("Finding Nemo", "Finding Dory")
    )
  )
)
df

# Extract only specified components
df %>% hoist(metadata,
  "species",
  first_film = list("films", 1L),
  third_film = list("films", 3L)
)