Subsetting

filter_scale

filter_scale(
    x: NestedScale,
    frame: str,
    unit: str | Sequence[str],
    drop_empty_frames: bool = False,
) -> NestedScale

Keep only the atoms belonging to unit at frame.

A real subset records coverage (per weight, of the root parent), parent_totals, parent_name, and is renamed "parent[frame:codes]". A filter that keeps every atom is a no-op.

prune_scale

prune_scale(x: NestedScale, frame: str) -> NestedScale

Collapse to a coarser frame: frame becomes the atom layer.

Weights are summed over the collapsed atoms; the result is renamed "name@frame". Atoms with no code at frame are dropped, and the loss shows in coverage.