Pivot data from wide to long — pivot_longer.tbl

pivot_longer() "lengthens" data, increasing the number of rows and decreasing the number of columns. The inverse transformation is tidyr::pivot_wider().

Learn more in vignette("pivot", "tidyr").

While most functionality is identical there are some differences to pivot_longer() on local data frames:

the output is sorted differently/not explicitly,
the coercion of mixed column types is left to the database,
values_ptypes NOT supported.

Note that build_longer_spec() and pivot_longer_spec() do not work with remote tables.

Usage

# S3 method for tbl_lazy
pivot_longer(
  data,
  cols,
  ...,
  cols_vary,
  names_to = "name",
  names_prefix = NULL,
  names_sep = NULL,
  names_pattern = NULL,
  names_ptypes = NULL,
  names_transform = NULL,
  names_repair = "check_unique",
  values_to = "value",
  values_drop_na = FALSE,
  values_ptypes,
  values_transform = NULL
)

Arguments

data: A data frame to pivot.
cols: Columns to pivot into longer format.
...: Additional arguments passed on to methods.
cols_vary: Unsupported; included for compatibility with the generic.
names_to: A string specifying the name of the column to create from the data stored in the column names of data.
names_prefix: A regular expression used to remove matching text from the start of each variable name.
names_sep, names_pattern: If names_to contains multiple values, these arguments control how the column name is broken up.
names_ptypes: A list of column name-prototype pairs.
names_transform, values_transform: A list of column name-function pairs.
names_repair: What happens if the output has invalid column names?
values_to: A string specifying the name of the column to create from the data stored in cell values. If names_to is a character containing the special .value sentinel, this value will be ignored, and the name of the value column will be derived from part of the existing column names.
values_drop_na: If TRUE, will drop rows that contain only NAs in the value_to column.
values_ptypes: Not supported.

Details

The SQL translation basically works as follows:

split the specification by its key columns i.e. by variables crammed into the column names.
for each part in the split specification transmute() data into the following columns

id columns i.e. columns that are not pivotted
key columns
value columns i.e. columns that are pivotted

combine all the parts with union_all()

Examples

# See vignette("pivot") for examples and explanation

# Simplest case where column names are character data
memdb_frame(
  id = c("a", "b"),
  x = 1:2,
  y = 3:4
) %>%
  tidyr::pivot_longer(-id)
#> # Source:   SQL [4 x 3]
#> # Database: sqlite 3.45.2 [:memory:]
#>   id    name  value
#>   <chr> <chr> <int>
#> 1 a     x         1
#> 2 b     x         2
#> 3 a     y         3
#> 4 b     y         4