Varying quantile by group is broken #20951
Description
Consider the following example:
df = pl.DataFrame(
{
"value": [1, 2, 1, 2],
"quantile": [0, 0, 1, 1],
}
)
df.group_by(pl.col.quantile).agg(pl.col.value.quantile(pl.col.quantile.first()))Output:
shape: (2, 2)
┌──────────┬───────┐
│ quantile ┆ value │
│ --- ┆ --- │
│ i64 ┆ f64 │
╞══════════╪═══════╡
│ 0 ┆ 1.0 │
│ 1 ┆ 1.0 │
└──────────┴───────┘
I would expect the value of the quantile = 1 group to be 2.0, not 1.0.