andrey.viz.layout#

andrey.viz.layout(structure, engine='auto', options=None)[source]#

Return the node positions draw() uses when none are given.

Pass the result as positions= to draw several structures over the same nodes, such as an estimate and its truth, with every node in the same place.

Parameters:

structure (GraphStructure) – Any kind.
engine (str) – "dot" lays the nodes out in ranks along the directed edges, causes on the left; "neato", "fdp", "sfdp", "circo", "twopi", "osage", and "patchwork" are Graphviz’s other layouts. These need pygraphviz, the viz extra. "builtin" needs nothing: nodes in layers along the directed edges, or on a circle when there are none or they form a cycle. "auto" is "dot" when pygraphviz is installed, and "builtin" otherwise.
options (Mapping[str, object] | None) – Graphviz graph attributes, such as {"rankdir": "TB"} to run causes top to bottom, or {"nodesep": 1} to spread nodes within a rank. The built-in layout takes none.

Returns:

Each node’s (x, y) in the unit square, y downward, in the layout’s proportions: the longer side spans the square, and the shorter one is centered.

Return type:

dict[int, tuple[float, float]]

Raises:

TypeError – If structure is not a GraphStructure, such as a TemporalStructure.
ValueError – If engine is not one of the above, or the built-in layout is given options.
ImportError – If a Graphviz engine is named and pygraphviz is not installed.

Examples

>>> import numpy as np
>>> from andrey.core.structure import GraphStructure, TAIL, ARROW
>>> import andrey.viz
>>> M = np.zeros((2, 2), np.int8); M[0, 1] = TAIL; M[1, 0] = ARROW  # X -> Y
>>> andrey.viz.layout(GraphStructure.from_numpy(M, kind="dag"), engine="builtin")
{0: (0.0, 0.5), 1: (1.0, 0.5)}