graph.py 文件源码

def laplacian(W, normalized=True):
    """Return the Laplacian of the weigth matrix."""

    # Degree matrix.
    d = W.sum(axis=0)

    # Laplacian matrix.
    if not normalized:
        D = scipy.sparse.diags(d.A.squeeze(), 0)
        L = D - W
    else:
        d += np.spacing(np.array(0, W.dtype))
        d = 1 / np.sqrt(d)
        D = scipy.sparse.diags(d.A.squeeze(), 0)
        I = scipy.sparse.identity(d.size, dtype=W.dtype)
        L = I - D * W * D

    # assert np.abs(L - L.T).mean() < 1e-9
    assert type(L) is scipy.sparse.csr.csr_matrix
    return L