Module « scipy.sparse.csgraph »

Fonction reconstruct_path - module scipy.sparse.csgraph

Signature de la fonction reconstruct_path

Description

reconstruct_path.__doc__

    reconstruct_path(csgraph, predecessors, directed=True)

    Construct a tree from a graph and a predecessor list.

    .. versionadded:: 0.11.0

    Parameters
    ----------
    csgraph : array_like or sparse matrix
        The N x N matrix representing the directed or undirected graph
        from which the predecessors are drawn.
    predecessors : array_like, one dimension
        The length-N array of indices of predecessors for the tree.  The
        index of the parent of node i is given by predecessors[i].
    directed : bool, optional
        If True (default), then operate on a directed graph: only move from
        point i to point j along paths csgraph[i, j].
        If False, then operate on an undirected graph: the algorithm can
        progress from point i to j along csgraph[i, j] or csgraph[j, i].

    Returns
    -------
    cstree : csr matrix
        The N x N directed compressed-sparse representation of the tree drawn
        from csgraph which is encoded by the predecessor list.

    Examples
    --------
    >>> from scipy.sparse import csr_matrix
    >>> from scipy.sparse.csgraph import reconstruct_path

    >>> graph = [
    ... [0, 1 , 2, 0],
    ... [0, 0, 0, 1],
    ... [0, 0, 0, 3],
    ... [0, 0, 0, 0]
    ... ]
    >>> graph = csr_matrix(graph)
    >>> print(graph)
      (0, 1)	1
      (0, 2)	2
      (1, 3)	1
      (2, 3)	3

    >>> pred = np.array([-9999, 0, 0, 1], dtype=np.int32)

    >>> cstree = reconstruct_path(csgraph=graph, predecessors=pred, directed=False)
    >>> cstree.todense()
    matrix([[ 0.,  1.,  2.,  0.],
            [ 0.,  0.,  0.,  1.],
            [ 0.,  0.,  0.,  0.],
            [ 0.,  0.,  0.,  0.]])