7  Masks and spatial context

cube_crop() reduces axes without changing retained values. cube_mask() preserves every axis and converts cells outside polygons to NA using cell-centre semantics. cube_polygon_weights() does not read cube values: it returns geometry intersections and fractions.

Operation	Preserves all axes	Modifies values	Returns cube	Semantics
crop	no	no	yes	domain reduction
mask	yes	yes (NA)	yes	cell centre
polygon weights	n/a	no values read	no	geometric fraction

stock_mask(), crop_stock(), and coast_dist() preserve established spatial-context workflows.