dfr n-unique for dataframe

Counts unique values.

Signature

> dfr n-unique

Input/output types:

input	output
any	any

Examples

Counts unique values

> [1 1 2 2 3 3 4] | dfr into-df | dfr n-unique
╭───┬──────────────╮
│ # │ count_unique │
├───┼──────────────┤
│ 0 │            4 │
╰───┴──────────────╯

Creates a is n-unique expression from a column

> dfr col a | dfr n-unique

Tips: Dataframe commands were not shipped in the official binaries by default, you have to build it with --features=dataframe flag