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# -*- coding: utf-8 -*-
# Copyright (c) Vispy Development Team. All Rights Reserved.
# Distributed under the (new) BSD License. See LICENSE.txt for more info.
"""
Random Graph Layout
====================
This layout positions the nodes at random
"""
import numpy as np
from ..util import _straight_line_vertices, issparse
def random(adjacency_mat, directed=False, random_state=None):
"""
Place the graph nodes at random places.
Parameters
----------
adjacency_mat : matrix or sparse
The graph adjacency matrix
directed : bool
Whether the graph is directed. If this is True, is will also
generate the vertices for arrows, which can be passed to an
ArrowVisual.
random_state : instance of RandomState | int | None
Random state to use. Can be None to use ``np.random``.
Yields
------
(node_vertices, line_vertices, arrow_vertices) : tuple
Yields the node and line vertices in a tuple. This layout only yields a
single time, and has no builtin animation
"""
if random_state is None:
random_state = np.random
elif not isinstance(random_state, np.random.RandomState):
random_state = np.random.RandomState(random_state)
if issparse(adjacency_mat):
adjacency_mat = adjacency_mat.tocoo()
# Randomly place nodes, visual coordinate system is between 0 and 1
num_nodes = adjacency_mat.shape[0]
node_coords = random_state.rand(num_nodes, 2)
line_vertices, arrows = _straight_line_vertices(adjacency_mat,
node_coords, directed)
yield node_coords, line_vertices, arrows
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