Transpose a DataFrame over the diagonal

Description

Usage

<DataFrame>$transpose(
  ...,
  include_header = FALSE,
  header_name = "column",
  column_names = NULL
)

Arguments

… These dots are for future extensions and must be empty.

include_header If set, the column names will be added as first column.

header_name If include_header is set, this determines the name of the column that will be inserted.

column_names Optional string naming an existing column, or a function that takes an integer vector representing the position of value (non-header) columns and returns a character vector of same length. Column position is 0-indexed.

Details

This is a very expensive operation. Perhaps you can do it differently.

Value

A polars DataFrame

Examples

library("polars")

df <- pl$DataFrame(a = c(1, 2, 3), b = c(4, 5, 6))
df$transpose(include_header = TRUE)

#> shape: (2, 4)
#> ┌────────┬──────────┬──────────┬──────────┐
#> │ column ┆ column_0 ┆ column_1 ┆ column_2 │
#> │ ---    ┆ ---      ┆ ---      ┆ ---      │
#> │ str    ┆ f64      ┆ f64      ┆ f64      │
#> ╞════════╪══════════╪══════════╪══════════╡
#> │ a      ┆ 1.0      ┆ 2.0      ┆ 3.0      │
#> │ b      ┆ 4.0      ┆ 5.0      ┆ 6.0      │
#> └────────┴──────────┴──────────┴──────────┘

# Replace the auto-generated column names with a list
df$transpose(include_header = FALSE, column_names = c("x", "y", "z"))

#> shape: (2, 3)
#> ┌─────┬─────┬─────┐
#> │ x   ┆ y   ┆ z   │
#> │ --- ┆ --- ┆ --- │
#> │ f64 ┆ f64 ┆ f64 │
#> ╞═════╪═════╪═════╡
#> │ 1.0 ┆ 2.0 ┆ 3.0 │
#> │ 4.0 ┆ 5.0 ┆ 6.0 │
#> └─────┴─────┴─────┘

# Include the header as a separate column
df$transpose(
  include_header = TRUE, header_name = "foo", column_names = c("x", "y", "z")
)

#> shape: (2, 4)
#> ┌─────┬─────┬─────┬─────┐
#> │ foo ┆ x   ┆ y   ┆ z   │
#> │ --- ┆ --- ┆ --- ┆ --- │
#> │ str ┆ f64 ┆ f64 ┆ f64 │
#> ╞═════╪═════╪═════╪═════╡
#> │ a   ┆ 1.0 ┆ 2.0 ┆ 3.0 │
#> │ b   ┆ 4.0 ┆ 5.0 ┆ 6.0 │
#> └─────┴─────┴─────┴─────┘

# Use a function to produce the new column names
name_generator <- function(x) {
  paste0("my_column_", x)
}
df$transpose(include_header = FALSE, column_names = name_generator)

#> shape: (2, 3)
#> ┌─────────────┬─────────────┬─────────────┐
#> │ my_column_0 ┆ my_column_1 ┆ my_column_2 │
#> │ ---         ┆ ---         ┆ ---         │
#> │ f64         ┆ f64         ┆ f64         │
#> ╞═════════════╪═════════════╪═════════════╡
#> │ 1.0         ┆ 2.0         ┆ 3.0         │
#> │ 4.0         ┆ 5.0         ┆ 6.0         │
#> └─────────────┴─────────────┴─────────────┘

# Use an existing column as the new column names
df <- pl$DataFrame(id = c("i", "j", "k"), a = c(1, 2, 3), b = c(4, 5, 6))
df$transpose(column_names = "id")

#> shape: (2, 3)
#> ┌─────┬─────┬─────┐
#> │ i   ┆ j   ┆ k   │
#> │ --- ┆ --- ┆ --- │
#> │ f64 ┆ f64 ┆ f64 │
#> ╞═════╪═════╪═════╡
#> │ 1.0 ┆ 2.0 ┆ 3.0 │
#> │ 4.0 ┆ 5.0 ┆ 6.0 │
#> └─────┴─────┴─────┘

df$transpose(include_header = TRUE, header_name = "new_id", column_names = "id")

#> shape: (2, 4)
#> ┌────────┬─────┬─────┬─────┐
#> │ new_id ┆ i   ┆ j   ┆ k   │
#> │ ---    ┆ --- ┆ --- ┆ --- │
#> │ str    ┆ f64 ┆ f64 ┆ f64 │
#> ╞════════╪═════╪═════╪═════╡
#> │ a      ┆ 1.0 ┆ 2.0 ┆ 3.0 │
#> │ b      ┆ 4.0 ┆ 5.0 ┆ 6.0 │
#> └────────┴─────┴─────┴─────┘