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Convert array to struct

Source code

Description

Convert array to struct

Usage

<Expr>$arr$to_struct(fields = NULL)

Arguments

fields If the name and number of the desired fields is known in advance, a list of field names can be given, which will be assigned by index. Otherwise, to dynamically assign field names, a custom R function that takes an R double and outputs a string value can be used. If NULL (default), fields will be field_0, field_1 … field_n.

Value

Expr

Examples

library("polars")

df = pl$DataFrame(
  values = list(1:3, c(2L, NA_integer_, 5L)),
  schema = list(values = pl$Array(pl$Int32, 3))
)
df$with_columns(
  struct = pl$col("values")$arr$to_struct()
)

#> shape: (2, 2)
#> ┌───────────────┬────────────┐
#> │ values        ┆ struct     │
#> │ ---           ┆ ---        │
#> │ array[i32, 3] ┆ struct[3]  │
#> ╞═══════════════╪════════════╡
#> │ [1, 2, 3]     ┆ {1,2,3}    │
#> │ [2, null, 5]  ┆ {2,null,5} │
#> └───────────────┴────────────┘

# pass a custom function that will name all fields by adding a prefix
df2 = df$with_columns(
  pl$col("values")$arr$to_struct(
    fields = \(idx) paste0("col_", idx)
  )
)
df2

#> shape: (2, 1)
#> ┌────────────┐
#> │ values     │
#> │ ---        │
#> │ struct[3]  │
#> ╞════════════╡
#> │ {1,2,3}    │
#> │ {2,null,5} │
#> └────────────┘

df2$unnest()

#> shape: (2, 3)
#> ┌───────┬───────┬───────┐
#> │ col_0 ┆ col_1 ┆ col_2 │
#> │ ---   ┆ ---   ┆ ---   │
#> │ i32   ┆ i32   ┆ i32   │
#> ╞═══════╪═══════╪═══════╡
#> │ 1     ┆ 2     ┆ 3     │
#> │ 2     ┆ null  ┆ 5     │
#> └───────┴───────┴───────┘