summarize

pydiverse.transform.summarize(**kwargs: ColExpr) → Pipeable

Computes aggregates over groups of rows.

Parameters:

kwargs – Each key is the name of a new column, and its value is the column expression defining the new column. The column expression may not contain columns that are neither part of the grouping columns nor wrapped in an aggregation function.

In contrast to mutate, this verb in general reduces the number of rows and only keeps the grouping columns and the new columns defined in the kwargs. One row for each unique combination of values in the grouping columns is created.

Examples

>>> t = pdt.Table(
...     {
...         "a": [1.2, 5.077, -2.29, -0.0, 3.0, -7.7],
...         "b": ["a  ", "transform", "pipedag", "cdegh", "  -ade ", "  pq"],
...         "c": [True, False, None, None, True, True],
...     }
... )
>>> (
...     t
...     >> group_by(t.c)
...     >> summarize(
...         u=t.b.str.len().mean(),
...         v=t.a.sum(filter=t.a >= 0),
...     )
...     >> show()
... )
shape: (3, 3)
┌───────┬──────────┬───────┐
│ c     ┆ u        ┆ v     │
│ ---   ┆ ---      ┆ ---   │
│ bool  ┆ f64      ┆ f64   │
╞═══════╪══════════╪═══════╡
│ true  ┆ 4.666667 ┆ 4.2   │
│ null  ┆ 6.0      ┆ -0.0  │
│ false ┆ 9.0      ┆ 5.077 │
└───────┴──────────┴───────┘