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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.
"""
Circular Layout
===============
This module contains several graph layouts which rely heavily on circles.
"""
import numpy as np
from ..util import _straight_line_vertices, issparse
def circular(adjacency_mat, directed=False):
"""Places all nodes on a single circle.
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.
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 issparse(adjacency_mat):
adjacency_mat = adjacency_mat.tocoo()
num_nodes = adjacency_mat.shape[0]
t = np.linspace(0, 2 * np.pi, num_nodes, endpoint=False)
# Visual coordinate system is between 0 and 1, so generate a circle with
# radius 0.5 and center it at the point (0.5, 0.5).
node_coords = (0.5 * np.array([np.cos(t), np.sin(t)]) + 0.5).T
node_coords = node_coords.astype(np.float32)
line_vertices, arrows = _straight_line_vertices(adjacency_mat,
node_coords, directed)
yield node_coords, line_vertices, arrows
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