# Precision / Recall Gate

### Description
Given a set of items (`SOURCE`) and a set of relevant items (`RELEVANT`),
lets `SOURCE` through only if the computed precision or recall is >= `Threshold`.
Otherwise, the empty set is returned.

### Input
- `SOURCE [OBJ]`: a list of objects
- `RELEVANT [OBJ]`: a list of objects

### Output
- `PRECISION [OBJ]:` `SOURCE` if precision is >= `Threshold`, an empty set otherwise
- `RECALL [OBJ]:` `SOURCE` if recall is >= `Threshold`, an empty set otherwise

### Parameters
- `Threshold` the minimum value requested for precision or recall to let `SOURCE` through.

Output scores can be [aggregated](docs://score_aggregation) and/or [normalised](docs://score_normalisation).