dfr get-ordinal for dataframe

Gets ordinal from date.

Signature

> dfr get-ordinal

Examples

Returns ordinal from a date

> let dt = ('2020-08-04T16:39:18+00:00' | into datetime -z 'UTC');
    let df = ([$dt $dt] | dfr into-df);
    $df | dfr get-ordinal
╭───┬─────╮
│ # │  0  │
├───┼─────┤
│ 0 │ 217 │
│ 1 │ 217 │
╰───┴─────╯