polars.Expr.pct_change

Expr.pct_change(
    n: int | IntoExprColumn = 1,
) → Expr

Computes percentage change between values.

Percentage change (as fraction) between current element and most-recent non-null element at least n period(s) before the current element.

Computes the change from the previous row by default.

engine:In Memory

Parameters:

n

periods to shift for forming percent change.

Notes

Null values are preserved. If you’re coming from pandas, this matches their fill_method=None behaviour.

Examples

>>> df = pl.DataFrame(
...     {
...         "a": [10, 11, 12, None, 12],
...     }
... )
>>> df.with_columns(pl.col("a").pct_change().alias("pct_change"))
shape: (5, 2)
┌──────┬────────────┐
│ a    ┆ pct_change │
│ ---  ┆ ---        │
│ i64  ┆ f64        │
╞══════╪════════════╡
│ 10   ┆ null       │
│ 11   ┆ 0.1        │
│ 12   ┆ 0.090909   │
│ null ┆ null       │
│ 12   ┆ null       │
└──────┴────────────┘