polars.Expr.rle_id#
- Expr.rle_id() Expr [source]#
Get a distinct integer ID for each run of identical values.
The ID starts at 0 and increases by one each time the value of the column changes.
- Returns:
- Expr
Expression of data type
UInt32
.
See also
Notes
This functionality is especially useful for defining a new group for every time a column’s value changes, rather than for every distinct value of that column.
Examples
>>> df = pl.DataFrame( ... { ... "a": [1, 2, 1, 1, 1], ... "b": ["x", "x", None, "y", "y"], ... } ... ) >>> df.with_columns( ... rle_id_a=pl.col("a").rle_id(), ... rle_id_ab=pl.struct("a", "b").rle_id(), ... ) shape: (5, 4) ┌─────┬──────┬──────────┬───────────┐ │ a ┆ b ┆ rle_id_a ┆ rle_id_ab │ │ --- ┆ --- ┆ --- ┆ --- │ │ i64 ┆ str ┆ u32 ┆ u32 │ ╞═════╪══════╪══════════╪═══════════╡ │ 1 ┆ x ┆ 0 ┆ 0 │ │ 2 ┆ x ┆ 1 ┆ 1 │ │ 1 ┆ null ┆ 2 ┆ 2 │ │ 1 ┆ y ┆ 2 ┆ 3 │ │ 1 ┆ y ┆ 2 ┆ 3 │ └─────┴──────┴──────────┴───────────┘