Expr.diff

methodView source ↗

def diff(n: int = 1) -> Expr

Categories: numeric

Compute the difference between an element value and the element value of the specified relative row.

It supports numberic and datetime types.

Parameters

parameter

n

The relative row to compute the difference with. Defaults to 1 (previous). Use a negative number to get a next row.

Examples

>>> import tabsdata as td
>>>
>>> tf: td.TableFrame ...
>>>
>>> tf.select(td.col("i"), td.col("i").diff().diff().alias("diff"))
>>>
┌──────┬──────┐
│ i    ┆ diff │
│ ---  ┆ ---  │
│ i64  ┆ i64  │
╞══════╪══════╡
│ 1    ┆ null │
│ 0    ┆ -1   │
│ 2    ┆ 2    │
│ 3    ┆ 1    │
│ 4    ┆ 1    │
│ -1   ┆ -5   │
│ -2   ┆ -1   │
│ -3   ┆ -1   │
│ -4   ┆ -1   │
│ -5   ┆ -1   │
│ null ┆ null │
└──────┴──────┘