Function khop_graph

python/dgl/transforms/functional.py:1178–1263

Return the graph whose edges connect the :attr:`k`-hop neighbors of the original graph. More specifically, an edge from node ``u`` and node ``v`` exists in the new graph if and only if a path with length :attr:`k` exists from node ``u`` to node ``v`` in the original graph. The adja

(g, k, copy_ndata=True)

def khop_graph(g, k, copy_ndata=True):
    """Return the graph whose edges connect the :attr:`k`-hop neighbors of the original graph.

    More specifically, an edge from node ``u`` and node ``v`` exists in the new graph if
    and only if a path with length :attr:`k` exists from node ``u`` to node ``v`` in the
    original graph.

    The adjacency matrix of the returned graph is :math:`A^k`
    (where :math:`A` is the adjacency matrix of :math:`g`).

    Parameters
    ----------
    g : DGLGraph
        The input graph.
    k : int
        The :math:`k` in `k`-hop graph.
    copy_ndata: bool, optional
        If True, the node features of the new graph are copied from the
        original graph.

        If False, the new graph will not have any node features.

        (Default: True)

    Returns
    -------
    DGLGraph
        The returned graph.

    Notes
    -----
    If :attr:`copy_ndata` is True, the resulting graph will share the node feature
    tensors with the input graph. Hence, users should try to avoid in-place operations
    which will be visible to both graphs.

    This function discards the batch information. Please use
    :func:`dgl.DGLGraph.set_batch_num_nodes`
    and :func:`dgl.DGLGraph.set_batch_num_edges` on the transformed graph
    to maintain the information.

    Examples
    --------

    Below gives an easy example:

    >>> import dgl
    >>> g = dgl.graph(([0, 1], [1, 2]))
    >>> g_2 = dgl.transforms.khop_graph(g, 2)
    >>> print(g_2.edges())
    (tensor([0]), tensor([2]))

    A more complicated example:

    >>> import dgl
    >>> g = dgl.graph(([0,1,2,3,4,0,1,2,3,4], [0,1,2,3,4,1,2,3,4,0]))
    >>> dgl.khop_graph(g, 1)
    DGLGraph(num_nodes=5, num_edges=10,
             ndata_schemes={}