Perform an asof join between this dataset and another one.

This is similar to a left-join except that we match on nearest key rather than equal keys. Both datasets must be sorted by the key. This type of join is most useful for time series data that are not perfectly aligned.

Optionally match on equivalent keys with “by” before searching with “on”.

Result of the join will be a new Dataset, where further operations can be applied.

Parameters:

right_dataset : dataset¶

The dataset to join to the current one, acting as the right dataset in the join operation.

on : str¶

The column from current dataset that should be used as the “on” key of the join operation left side.

An inexact match is used on the “on” key, i.e. a row is considered a match if and only if left_on - tolerance <= right_on <= left_on.

The input table must be sorted by the “on” key. Must be a single field of a common type.

Currently, the “on” key must be an integer, date, or timestamp type.

by : str or list[str]¶

The columns from current dataset that should be used as the keys of the join operation left side. The join operation is then done only for the matches in these columns.

tolerance : int¶

The tolerance for inexact “on” key matching. A right row is considered a match with the left row right.on - left.on <= tolerance. The tolerance may be:

• negative, in which case a past-as-of-join occurs;

• or positive, in which case a future-as-of-join occurs;

• or zero, in which case an exact-as-of-join occurs.

The tolerance is interpreted in the same units as the “on” key.

right_on : str or list[str], default None¶

The columns from the right_dataset that should be used as the on key on the join operation right side. When None use the same key name as the left dataset.

right_by : str or list[str], default None¶

The columns from the right_dataset that should be used as by keys on the join operation right side. When None use the same key names as the left dataset.

Return type:

InMemoryDataset