Class representing a cover of an arbitrary ordered set.

Covers are similar to clusterings, but each element of the set may belong to more than one cluster in a cover, and elements not belonging to any cluster are also allowed.

Cover instances provide a similar API as Clustering instances; for instance, iterating over a Cover will iterate over the clusters just like with a regular Clustering instance. However, they are not derived from each other or from a common superclass, and there might be functions that exist only in one of them or the other.

Clusters of an individual cover can be accessed by the [] operator:

>>> cl = Cover([[0,1,2,3], [2,3,4], [0,1,6]])
>>> cl[0]
[0, 1, 2, 3]

The membership vector can be accessed by the membership property. Note that contrary to Clustering instances, the membership vector will contain lists that contain the cluster indices each item belongs to:

>>> cl.membership
[[0, 2], [0, 2], [0, 1], [0, 1], [1], [], [2]]

The number of clusters can be retrieved by the len function:

>>> len(cl)
3

You can iterate over the cover as if it were a regular list of clusters:

>>> for cluster in cl:
...     print(" ".join(str(idx) for idx in cluster))
...
0 1 2 3
2 3 4
0 1 6

If you need all the clusters at once as lists, you can simply convert the cover to a list:

>>> cluster_list = list(cl)
>>> print(cluster_list)
[[0, 1, 2, 3], [2, 3, 4], [0, 1, 6]]

Clustering objects can readily be converted to Cover objects using the constructor:

>>> clustering = Clustering([0, 0, 0, 0, 1, 1, 1, 2, 2, 2])
>>> cover = Cover(clustering)
>>> list(clustering) == list(cover)
True