#### 3.5 Selecting and Ordering

Selecting a subset of elements in one or several dimension results in a datacube of the same
dimension with fewer tuples. This operation can be neatly integrated into a visualisation tool of
datacube. Another similar operation is ordering: The elements in one or several dimension are
sorted along a criterion. For example, a distance matrix can be sorted in the order of
the distance (global sorting) to get the 5 shortest distance in the matrix, but one
could also sort it along one dimension (dimensional sorting), to get the 5 closest
neighbors of each location. This may be interesting in a heuristic to find a good TSP
tour.