"""

Module for creating Sankey diagrams using Matplotlib.

"""

import logging

from types import SimpleNamespace

import numpy as np

import matplotlib as mpl

from matplotlib.path import Path

from matplotlib.patches import PathPatch

from matplotlib.transforms import Affine2D

from matplotlib import _docstring

_log = logging.getLogger(__name__)

__author__ = "Kevin L. Davies"

__credits__ = ["Yannick Copin"]

__license__ = "BSD"

__version__ = "2011/09/16"

# Angles [deg/90]

RIGHT = 0

UP = 1

# LEFT = 2

DOWN = 3

class Sankey:

"""

Sankey diagram.

Sankey diagrams are a specific type of flow diagram, in which

the width of the arrows is shown proportionally to the flow

quantity. They are typically used to visualize energy or

material or cost transfers between processes.

`Wikipedia (6/1/2011) <https://en.wikipedia.org/wiki/Sankey_diagram>`_

"""

def __init__(self, ax=None, scale=1.0, unit='', format='%G', gap=0.25,

radius=0.1, shoulder=0.03, offset=0.15, head_angle=100,

margin=0.4, tolerance=1e-6, **kwargs):

"""

Create a new Sankey instance.

The optional arguments listed below are applied to all subdiagrams so

that there is consistent alignment and formatting.

In order to draw a complex Sankey diagram, create an instance of

`Sankey` by calling it without any kwargs::

sankey = Sankey()

Then add simple Sankey sub-diagrams::

sankey.add() # 1

sankey.add() # 2

#...

sankey.add() # n

Finally, create the full diagram::

sankey.finish()

Or, instead, simply daisy-chain those calls::

Sankey().add().add... .add().finish()

Other Parameters

----------------

ax : `~matplotlib.axes.Axes`

Axes onto which the data should be plotted. If *ax* isn't

provided, new Axes will be created.

scale : float

Scaling factor for the flows. *scale* sizes the width of the paths

in order to maintain proper layout. The same scale is applied to

all subdiagrams. The value should be chosen such that the product

of the scale and the sum of the inputs is approximately 1.0 (and

the product of the scale and the sum of the outputs is

approximately -1.0).

unit : str

The physical unit associated with the flow quantities. If *unit*

is None, then none of the quantities are labeled.

format : str or callable

A Python number formatting string or callable used to label the

flows with their quantities (i.e., a number times a unit, where the

unit is given). If a format string is given, the label will be

``format % quantity``. If a callable is given, it will be called

with ``quantity`` as an argument.

gap : float

Space between paths that break in/break away to/from the top or

bottom.

radius : float

Inner radius of the vertical paths.

shoulder : float

Size of the shoulders of output arrows.

offset : float

Text offset (from the dip or tip of the arrow).

head_angle : float

Angle, in degrees, of the arrow heads (and negative of the angle of

the tails).

margin : float

Minimum space between Sankey outlines and the edge of the plot

area.

tolerance : float

Acceptable maximum of the magnitude of the sum of flows. The

magnitude of the sum of connected flows cannot be greater than

*tolerance*.

**kwargs

Any additional keyword arguments will be passed to `add`, which

will create the first subdiagram.

See Also

--------

Sankey.add

Sankey.finish

Examples

--------

.. plot:: gallery/specialty_plots/sankey_basics.py

"""

# Check the arguments.

if gap < 0:

raise ValueError(

"'gap' is negative, which is not allowed because it would "

"cause the paths to overlap")

if radius > gap:

raise ValueError(

"'radius' is greater than 'gap', which is not allowed because "

"it would cause the paths to overlap")

if head_angle < 0:

raise ValueError(

"'head_angle' is negative, which is not allowed because it "

"would cause inputs to look like outputs and vice versa")

if tolerance < 0:

raise ValueError(

"'tolerance' is negative, but it must be a magnitude")

# Create Axes if necessary.

if ax is None:

import matplotlib.pyplot as plt

fig = plt.figure()

ax = fig.add_subplot(1, 1, 1, xticks=[], yticks=[])

self.diagrams = []

# Store the inputs.

self.ax = ax

self.unit = unit

self.format = format

self.scale = scale

self.gap = gap

self.radius = radius

self.shoulder = shoulder

self.offset = offset

self.margin = margin

self.pitch = np.tan(np.pi * (1 - head_angle / 180.0) / 2.0)

self.tolerance = tolerance

# Initialize the vertices of tight box around the diagram(s).

self.extent = np.array((np.inf, -np.inf, np.inf, -np.inf))

# If there are any kwargs, create the first subdiagram.

if len(kwargs):

self.add(**kwargs)

def _arc(self, quadrant=0, cw=True, radius=1, center=(0, 0)):

"""

Return the codes and vertices for a rotated, scaled, and translated

90 degree arc.

Other Parameters

----------------

quadrant : {0, 1, 2, 3}, default: 0

Uses 0-based indexing (0, 1, 2, or 3).

cw : bool, default: True

If True, the arc vertices are produced clockwise; counter-clockwise

otherwise.

radius : float, default: 1

The radius of the arc.

center : (float, float), default: (0, 0)

(x, y) tuple of the arc's center.

"""

# Note: It would be possible to use matplotlib's transforms to rotate,

# scale, and translate the arc, but since the angles are discrete,

# it's just as easy and maybe more efficient to do it here.

ARC_CODES = [Path.LINETO,

Path.CURVE4,

Path.CURVE4,

Path.CURVE4,

Path.CURVE4,

Path.CURVE4,

Path.CURVE4]

# Vertices of a cubic Bezier curve approximating a 90 deg arc

# These can be determined by Path.arc(0, 90).

ARC_VERTICES = np.array([[1.00000000e+00, 0.00000000e+00],

[1.00000000e+00, 2.65114773e-01],

[8.94571235e-01, 5.19642327e-01],

[7.07106781e-01, 7.07106781e-01],

[5.19642327e-01, 8.94571235e-01],

[2.65114773e-01, 1.00000000e+00],

# Insignificant

# [6.12303177e-17, 1.00000000e+00]])

[0.00000000e+00, 1.00000000e+00]])

if quadrant in (0, 2):

if cw:

vertices = ARC_VERTICES

else:

vertices = ARC_VERTICES[:, ::-1] # Swap x and y.

else: # 1, 3

# Negate x.

if cw:

# Swap x and y.

vertices = np.column_stack((-ARC_VERTICES[:, 1],

ARC_VERTICES[:, 0]))

else:

vertices = np.column_stack((-ARC_VERTICES[:, 0],

ARC_VERTICES[:, 1]))

if quadrant > 1:

radius = -radius # Rotate 180 deg.

return list(zip(ARC_CODES, radius * vertices +

np.tile(center, (ARC_VERTICES.shape[0], 1))))

def _add_input(self, path, angle, flow, length):

"""

Add an input to a path and return its tip and label locations.

"""

if angle is None:

return [0, 0], [0, 0]

else:

x, y = path[-1][1] # Use the last point as a reference.

dipdepth = (flow / 2) * self.pitch

if angle == RIGHT:

x -= length

dip = [x + dipdepth, y + flow / 2.0]

path.extend([(Path.LINETO, [x, y]),

(Path.LINETO, dip),

(Path.LINETO, [x, y + flow]),

(Path.LINETO, [x + self.gap, y + flow])])

label_location = [dip[0] - self.offset, dip[1]]

else: # Vertical

x -= self.gap

if angle == UP:

sign = 1

else:

sign = -1

dip = [x - flow / 2, y - sign * (length - dipdepth)]

if angle == DOWN:

quadrant = 2

else:

quadrant = 1

# Inner arc isn't needed if inner radius is zero

if self.radius:

path.extend(self._arc(quadrant=quadrant,

cw=angle == UP,

radius=self.radius,

center=(x + self.radius,

y - sign * self.radius)))

else:

path.append((Path.LINETO, [x, y]))

path.extend([(Path.LINETO, [x, y - sign * length]),

(Path.LINETO, dip),

(Path.LINETO, [x - flow, y - sign * length])])

path.extend(self._arc(quadrant=quadrant,

cw=angle == DOWN,

radius=flow + self.radius,

center=(x + self.radius,

y - sign * self.radius)))

path.append((Path.LINETO, [x - flow, y + sign * flow]))

label_location = [dip[0], dip[1] - sign * self.offset]

return dip, label_location

def _add_output(self, path, angle, flow, length):

"""

Append an output to a path and return its tip and label locations.

.. note:: *flow* is negative for an output.

"""

if angle is None:

return [0, 0], [0, 0]

else:

x, y = path[-1][1] # Use the last point as a reference.

tipheight = (self.shoulder - flow / 2) * self.pitch

if angle == RIGHT:

x += length

tip = [x + tipheight, y + flow / 2.0]

path.extend([(Path.LINETO, [x, y]),

(Path.LINETO, [x, y + self.shoulder]),

(Path.LINETO, tip),

(Path.LINETO, [x, y - self.shoulder + flow]),

(Path.LINETO, [x, y + flow]),

(Path.LINETO, [x - self.gap, y + flow])])

label_location = [tip[0] + self.offset, tip[1]]

else: # Vertical

x += self.gap

if angle == UP:

sign, quadrant = 1, 3

else:

sign, quadrant = -1, 0

tip = [x - flow / 2.0, y + sign * (length + tipheight)]

# Inner arc isn't needed if inner radius is zero

if self.radius:

path.extend(self._arc(quadrant=quadrant,

cw=angle == UP,

radius=self.radius,

center=(x - self.radius,

y + sign * self.radius)))

else:

path.append((Path.LINETO, [x, y]))

path.extend([(Path.LINETO, [x, y + sign * length]),

(Path.LINETO, [x - self.shoulder,

y + sign * length]),

(Path.LINETO, tip),

(Path.LINETO, [x + self.shoulder - flow,

y + sign * length]),

(Path.LINETO, [x - flow, y + sign * length])])

path.extend(self._arc(quadrant=quadrant,

cw=angle == DOWN,

radius=self.radius - flow,

center=(x - self.radius,

y + sign * self.radius)))

path.append((Path.LINETO, [x - flow, y + sign * flow]))

label_location = [tip[0], tip[1] + sign * self.offset]

return tip, label_location

def _revert(self, path, first_action=Path.LINETO):

"""

A path is not simply reversible by path[::-1] since the code

specifies an action to take from the **previous** point.

"""

reverse_path = []

next_code = first_action

for code, position in path[::-1]:

reverse_path.append((next_code, position))

next_code = code

return reverse_path

# This might be more efficient, but it fails because 'tuple' object

# doesn't support item assignment:

# path[1] = path[1][-1:0:-1]

# path[1][0] = first_action

# path[2] = path[2][::-1]

# return path

@_docstring.interpd

def add(self, patchlabel='', flows=None, orientations=None, labels='',

trunklength=1.0, pathlengths=0.25, prior=None, connect=(0, 0),

rotation=0, **kwargs):

"""

Add a simple Sankey diagram with flows at the same hierarchical level.

Parameters

----------

patchlabel : str

Label to be placed at the center of the diagram.

Note that *label* (not *patchlabel*) can be passed as keyword

argument to create an entry in the legend.

flows : list of float

Array of flow values. By convention, inputs are positive and

outputs are negative.

Flows are placed along the top of the diagram from the inside out

in order of their index within *flows*. They are placed along the

sides of the diagram from the top down and along the bottom from

the outside in.

If the sum of the inputs and outputs is

nonzero, the discrepancy will appear as a cubic Bézier curve along

the top and bottom edges of the trunk.

orientations : list of {-1, 0, 1}

List of orientations of the flows (or a single orientation to be

used for all flows). Valid values are 0 (inputs from

the left, outputs to the right), 1 (from and to the top) or -1

(from and to the bottom).

labels : list of (str or None)

List of labels for the flows (or a single label to be used for all

flows). Each label may be *None* (no label), or a labeling string.

If an entry is a (possibly empty) string, then the quantity for the

corresponding flow will be shown below the string. However, if

the *unit* of the main diagram is None, then quantities are never

shown, regardless of the value of this argument.

trunklength : float

Length between the bases of the input and output groups (in

data-space units).

pathlengths : list of float

List of lengths of the vertical arrows before break-in or after

break-away. If a single value is given, then it will be applied to

the first (inside) paths on the top and bottom, and the length of

all other arrows will be justified accordingly. The *pathlengths*

are not applied to the horizontal inputs and outputs.

prior : int

Index of the prior diagram to which this diagram should be

connected.

connect : (int, int)

A (prior, this) tuple indexing the flow of the prior diagram and

the flow of this diagram which should be connected. If this is the

first diagram or *prior* is *None*, *connect* will be ignored.

rotation : float

Angle of rotation of the diagram in degrees. The interpretation of

the *orientations* argument will be rotated accordingly (e.g., if

*rotation* == 90, an *orientations* entry of 1 means to/from the

left). *rotation* is ignored if this diagram is connected to an

existing one (using *prior* and *connect*).

Returns

-------

Sankey

The current `.Sankey` instance.

Other Parameters

----------------

**kwargs

Additional keyword arguments set `matplotlib.patches.PathPatch`

properties, listed below. For example, one may want to use

``fill=False`` or ``label="A legend entry"``.

%(Patch:kwdoc)s

See Also

--------

Sankey.finish

"""

# Check and preprocess the arguments.

flows = np.array([1.0, -1.0]) if flows is None else np.array(flows)

n = flows.shape[0] # Number of flows

if rotation is None:

rotation = 0

else:

# In the code below, angles are expressed in deg/90.

rotation /= 90.0

if orientations is None:

orientations = 0

try:

orientations = np.broadcast_to(orientations, n)

except ValueError:

raise ValueError(

f"The shapes of 'flows' {np.shape(flows)} and 'orientations' "

f"{np.shape(orientations)} are incompatible"

) from None

try:

labels = np.broadcast_to(labels, n)

except ValueError:

raise ValueError(

f"The shapes of 'flows' {np.shape(flows)} and 'labels' "

f"{np.shape(labels)} are incompatible"

) from None

if trunklength < 0:

raise ValueError(

"'trunklength' is negative, which is not allowed because it "

"would cause poor layout")

if abs(np.sum(flows)) > self.tolerance:

_log.info("The sum of the flows is nonzero (%f; patchlabel=%r); "

"is the system not at steady state?",

np.sum(flows), patchlabel)

scaled_flows = self.scale * flows

gain = sum(max(flow, 0) for flow in scaled_flows)

loss = sum(min(flow, 0) for flow in scaled_flows)

if prior is not None:

if prior < 0:

raise ValueError("The index of the prior diagram is negative")

if min(connect) < 0:

raise ValueError(

"At least one of the connection indices is negative")

if prior >= len(self.diagrams):

raise ValueError(

f"The index of the prior diagram is {prior}, but there "

f"are only {len(self.diagrams)} other diagrams")

if connect[0] >= len(self.diagrams[prior].flows):

raise ValueError(

"The connection index to the source diagram is {}, but "

"that diagram has only {} flows".format(

connect[0], len(self.diagrams[prior].flows)))

if connect[1] >= n:

raise ValueError(

f"The connection index to this diagram is {connect[1]}, "

f"but this diagram has only {n} flows")

if self.diagrams[prior].angles[connect[0]] is None:

raise ValueError(

f"The connection cannot be made, which may occur if the "

f"magnitude of flow {connect[0]} of diagram {prior} is "

f"less than the specified tolerance")

flow_error = (self.diagrams[prior].flows[connect[0]] +

flows[connect[1]])

if abs(flow_error) >= self.tolerance:

raise ValueError(

f"The scaled sum of the connected flows is {flow_error}, "

f"which is not within the tolerance ({self.tolerance})")

# Determine if the flows are inputs.

are_inputs = [None] * n

for i, flow in enumerate(flows):

if flow >= self.tolerance:

are_inputs[i] = True

elif flow <= -self.tolerance:

are_inputs[i] = False

else:

_log.info(

"The magnitude of flow %d (%f) is below the tolerance "

"(%f).\nIt will not be shown, and it cannot be used in a "

"connection.", i, flow, self.tolerance)

# Determine the angles of the arrows (before rotation).

angles = [None] * n

for i, (orient, is_input) in enumerate(zip(orientations, are_inputs)):

if orient == 1:

if is_input:

angles[i] = DOWN

elif is_input is False:

# Be specific since is_input can be None.

angles[i] = UP

elif orient == 0:

if is_input is not None:

angles[i] = RIGHT

else:

if orient != -1:

raise ValueError(

f"The value of orientations[{i}] is {orient}, "

f"but it must be -1, 0, or 1")

if is_input:

angles[i] = UP

elif is_input is False:

angles[i] = DOWN

# Justify the lengths of the paths.

if np.iterable(pathlengths):

if len(pathlengths) != n:

raise ValueError(

f"The lengths of 'flows' ({n}) and 'pathlengths' "

f"({len(pathlengths)}) are incompatible")

else: # Make pathlengths into a list.

urlength = pathlengths

ullength = pathlengths

lrlength = pathlengths

lllength = pathlengths

d = dict(RIGHT=pathlengths)

pathlengths = [d.get(angle, 0) for angle in angles]

# Determine the lengths of the top-side arrows

# from the middle outwards.

for i, (angle, is_input, flow) in enumerate(zip(angles, are_inputs,

scaled_flows)):

if angle == DOWN and is_input:

pathlengths[i] = ullength

ullength += flow

elif angle == UP and is_input is False:

pathlengths[i] = urlength

urlength -= flow # Flow is negative for outputs.

# Determine the lengths of the bottom-side arrows

# from the middle outwards.

for i, (angle, is_input, flow) in enumerate(reversed(list(zip(

angles, are_inputs, scaled_flows)))):

if angle == UP and is_input:

pathlengths[n - i - 1] = lllength

lllength += flow

elif angle == DOWN and is_input is False:

pathlengths[n - i - 1] = lrlength

lrlength -= flow

# Determine the lengths of the left-side arrows

# from the bottom upwards.

has_left_input = False

for i, (angle, is_input, spec) in enumerate(reversed(list(zip(

angles, are_inputs, zip(scaled_flows, pathlengths))))):

if angle == RIGHT:

if is_input:

if has_left_input:

pathlengths[n - i - 1] = 0

else:

has_left_input = True

# Determine the lengths of the right-side arrows

# from the top downwards.

has_right_output = False

for i, (angle, is_input, spec) in enumerate(zip(

angles, are_inputs, list(zip(scaled_flows, pathlengths)))):

if angle == RIGHT:

if is_input is False:

if has_right_output:

pathlengths[i] = 0

else:

has_right_output = True

# Begin the subpaths, and smooth the transition if the sum of the flows

# is nonzero.

urpath = [(Path.MOVETO, [(self.gap - trunklength / 2.0), # Upper right

gain / 2.0]),

(Path.LINETO, [(self.gap - trunklength / 2.0) / 2.0,

gain / 2.0]),

(Path.CURVE4, [(self.gap - trunklength / 2.0) / 8.0,

gain / 2.0]),

(Path.CURVE4, [(trunklength / 2.0 - self.gap) / 8.0,

-loss / 2.0]),

(Path.LINETO, [(trunklength / 2.0 - self.gap) / 2.0,

-loss / 2.0]),

(Path.LINETO, [(trunklength / 2.0 - self.gap),

-loss / 2.0])]

llpath = [(Path.LINETO, [(trunklength / 2.0 - self.gap), # Lower left

loss / 2.0]),

(Path.LINETO, [(trunklength / 2.0 - self.gap) / 2.0,

loss / 2.0]),

(Path.CURVE4, [(trunklength / 2.0 - self.gap) / 8.0,

loss / 2.0]),

(Path.CURVE4, [(self.gap - trunklength / 2.0) / 8.0,

-gain / 2.0]),

(Path.LINETO, [(self.gap - trunklength / 2.0) / 2.0,

-gain / 2.0]),

(Path.LINETO, [(self.gap - trunklength / 2.0),

-gain / 2.0])]

lrpath = [(Path.LINETO, [(trunklength / 2.0 - self.gap), # Lower right

loss / 2.0])]

ulpath = [(Path.LINETO, [self.gap - trunklength / 2.0, # Upper left

gain / 2.0])]

# Add the subpaths and assign the locations of the tips and labels.

tips = np.zeros((n, 2))

label_locations = np.zeros((n, 2))

# Add the top-side inputs and outputs from the middle outwards.

for i, (angle, is_input, spec) in enumerate(zip(

angles, are_inputs, list(zip(scaled_flows, pathlengths)))):

if angle == DOWN and is_input:

tips[i, :], label_locations[i, :] = self._add_input(

ulpath, angle, *spec)

elif angle == UP and is_input is False:

tips[i, :], label_locations[i, :] = self._add_output(

urpath, angle, *spec)

# Add the bottom-side inputs and outputs from the middle outwards.

for i, (angle, is_input, spec) in enumerate(reversed(list(zip(

angles, are_inputs, list(zip(scaled_flows, pathlengths)))))):

if angle == UP and is_input:

tip, label_location = self._add_input(llpath, angle, *spec)

tips[n - i - 1, :] = tip

label_locations[n - i - 1, :] = label_location

elif angle == DOWN and is_input is False:

tip, label_location = self._add_output(lrpath, angle, *spec)

tips[n - i - 1, :] = tip

label_locations[n - i - 1, :] = label_location

# Add the left-side inputs from the bottom upwards.

has_left_input = False

for i, (angle, is_input, spec) in enumerate(reversed(list(zip(

angles, are_inputs, list(zip(scaled_flows, pathlengths)))))):

if angle == RIGHT and is_input:

if not has_left_input:

# Make sure the lower path extends

# at least as far as the upper one.

if llpath[-1][1][0] > ulpath[-1][1][0]:

llpath.append((Path.LINETO, [ulpath[-1][1][0],

llpath[-1][1][1]]))

has_left_input = True

tip, label_location = self._add_input(llpath, angle, *spec)

tips[n - i - 1, :] = tip

label_locations[n - i - 1, :] = label_location

# Add the right-side outputs from the top downwards.

has_right_output = False

for i, (angle, is_input, spec) in enumerate(zip(

angles, are_inputs, list(zip(scaled_flows, pathlengths)))):

if angle == RIGHT and is_input is False:

if not has_right_output:

# Make sure the upper path extends

# at least as far as the lower one.

if urpath[-1][1][0] < lrpath[-1][1][0]:

urpath.append((Path.LINETO, [lrpath[-1][1][0],

urpath[-1][1][1]]))

has_right_output = True

tips[i, :], label_locations[i, :] = self._add_output(

urpath, angle, *spec)

# Trim any hanging vertices.

if not has_left_input:

ulpath.pop()

llpath.pop()

if not has_right_output:

lrpath.pop()

urpath.pop()

# Concatenate the subpaths in the correct order (clockwise from top).

path = (urpath + self._revert(lrpath) + llpath + self._revert(ulpath) +

[(Path.CLOSEPOLY, urpath[0][1])])

# Create a patch with the Sankey outline.

codes, vertices = zip(*path)

vertices = np.array(vertices)

def _get_angle(a, r):

if a is None:

return None

else:

return a + r

if prior is None:

if rotation != 0: # By default, none of this is needed.

angles = [_get_angle(angle, rotation) for angle in angles]

rotate = Affine2D().rotate_deg(rotation * 90).transform_affine

tips = rotate(tips)

label_locations = rotate(label_locations)

vertices = rotate(vertices)

text = self.ax.text(0, 0, s=patchlabel, ha='center', va='center')

else:

rotation = (self.diagrams[prior].angles[connect[0]] -

angles[connect[1]])

angles = [_get_angle(angle, rotation) for angle in angles]

rotate = Affine2D().rotate_deg(rotation * 90).transform_affine

tips = rotate(tips)

offset = self.diagrams[prior].tips[connect[0]] - tips[connect[1]]

translate = Affine2D().translate(*offset).transform_affine

tips = translate(tips)

label_locations = translate(rotate(label_locations))

vertices = translate(rotate(vertices))

kwds = dict(s=patchlabel, ha='center', va='center')

text = self.ax.text(*offset, **kwds)

if mpl.rcParams['_internal.classic_mode']:

fc = kwargs.pop('fc', kwargs.pop('facecolor', '#bfd1d4'))

lw = kwargs.pop('lw', kwargs.pop('linewidth', 0.5))

else:

fc = kwargs.pop('fc', kwargs.pop('facecolor', None))

lw = kwargs.pop('lw', kwargs.pop('linewidth', None))

if fc is None:

fc = self.ax._get_patches_for_fill.get_next_color()

patch = PathPatch(Path(vertices, codes), fc=fc, lw=lw, **kwargs)

self.ax.add_patch(patch)

# Add the path labels.

texts = []

for number, angle, label, location in zip(flows, angles, labels,

label_locations):

if label is None or angle is None:

label = ''

elif self.unit is not None:

if isinstance(self.format, str):

quantity = self.format % abs(number) + self.unit

elif callable(self.format):

quantity = self.format(number)

else:

raise TypeError(

'format must be callable or a format string')

if label != '':

label += "\n"

label += quantity

texts.append(self.ax.text(x=location[0], y=location[1],

s=label,

ha='center', va='center'))

# Text objects are placed even they are empty (as long as the magnitude

# of the corresponding flow is larger than the tolerance) in case the

# user wants to provide labels later.

# Expand the size of the diagram if necessary.

self.extent = (min(np.min(vertices[:, 0]),

np.min(label_locations[:, 0]),

self.extent[0]),

max(np.max(vertices[:, 0]),

np.max(label_locations[:, 0]),

self.extent[1]),

min(np.min(vertices[:, 1]),

np.min(label_locations[:, 1]),

self.extent[2]),

max(np.max(vertices[:, 1]),

np.max(label_locations[:, 1]),

self.extent[3]))

# Include both vertices _and_ label locations in the extents; there are

# where either could determine the margins (e.g., arrow shoulders).

# Add this diagram as a subdiagram.

self.diagrams.append(

SimpleNamespace(patch=patch, flows=flows, angles=angles, tips=tips,

text=text, texts=texts))

# Allow a daisy-chained call structure (see docstring for the class).

return self

def finish(self):

"""

Adjust the Axes and return a list of information about the Sankey

subdiagram(s).

Returns a list of subdiagrams with the following fields:

======== =============================================================

Field Description

======== =============================================================

*patch* Sankey outline (a `~matplotlib.patches.PathPatch`).

*flows* Flow values (positive for input, negative for output).

*angles* List of angles of the arrows [deg/90].

For example, if the diagram has not been rotated,

an input to the top side has an angle of 3 (DOWN),

and an output from the top side has an angle of 1 (UP).

If a flow has been skipped (because its magnitude is less

than *tolerance*), then its angle will be *None*.

*tips* (N, 2)-array of the (x, y) positions of the tips (or "dips")

of the flow paths.

If the magnitude of a flow is less the *tolerance* of this

`Sankey` instance, the flow is skipped and its tip will be at

the center of the diagram.

*text* `.Text` instance for the diagram label.

*texts* List of `.Text` instances for the flow labels.

======== =============================================================

See Also

--------

Sankey.add

"""

self.ax.axis([self.extent[0] - self.margin,

self.extent[1] + self.margin,

self.extent[2] - self.margin,

self.extent[3] + self.margin])

self.ax.set_aspect('equal', adjustable='datalim')

return self.diagrams