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#!/usr/bin/env python
"""
Module for creating Sankey diagrams using matplotlib
"""
__author__ = "Kevin L. Davies"
__credits__ = ["Yannick Copin"]
__license__ = "BSD"
__version__ = "2011/09/16"
# Original version by Yannick Copin (ycopin@ipnl.in2p3.fr) 10/2/2010, available
# at:
# http://matplotlib.org/examples/api/sankey_demo_old.html
# Modifications by Kevin Davies (kld@alumni.carnegiemellon.edu) 6/3/2011:
# --Used arcs for the curves (so that the widths of the paths are uniform)
# --Converted the function to a class and created methods to join
# multiple simple Sankey diagrams
# --Provided handling for cases where the total of the inputs isn't 100
# Now, the default layout is based on the assumption that the inputs sum to
# 1. A scaling parameter can be used in other cases.
# --The call structure was changed to be more explicit about layout,
# including the length of the trunk, length of the paths, gap between the
# paths, and the margin around the diagram.
# --Allowed the lengths of paths to be adjusted individually, with an option
# to automatically justify them
# --The call structure was changed to make the specification of path
# orientation more flexible. Flows are passed through one array, with
# inputs being positive and outputs being negative. An orientation
# argument specifies the direction of the arrows. The "main"
# inputs/outputs are now specified via an orientation of 0, and there may
# be several of each.
# --Added assertions to catch common calling errors
# -Added the physical unit as a string argument to be used in the labels, so
# that the values of the flows can usually be applied automatically
# --Added an argument for a minimum magnitude below which flows are not shown
# --Added a tapered trunk in the case that the flows do not sum to 0
# --Allowed the diagram to be rotated
import numpy as np
from matplotlib.cbook import iterable, Bunch
from matplotlib.path import Path
from matplotlib.patches import PathPatch
from matplotlib.transforms import Affine2D
from matplotlib import verbose
from matplotlib import docstring
# Angles [deg/90]
RIGHT = 0
UP = 1
# LEFT = 2
DOWN = 3
class Sankey:
"""
Sankey diagram in matplotlib
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) <http://en.wikipedia.org/wiki/Sankey_diagram>`_
"""
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.
Optional keyword arguments:
=============== ==========================================
Keyword Description
=============== ==========================================
*quadrant* uses 0-based indexing (0, 1, 2, or 3)
*cw* if True, clockwise
*center* (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 == 0 or quadrant == 2:
if cw:
vertices = ARC_VERTICES
else:
vertices = ARC_VERTICES[:, ::-1] # Swap x and y.
elif quadrant == 1 or quadrant == 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 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 = 1
else:
sign = -1
tip = [x - flow / 2.0, y + sign * (length + tipheight)]
if angle == UP:
quadrant = 3
else:
quadrant = 0
# 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 revertable 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.dedent_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.
Return value is the instance of :class:`Sankey`.
Optional keyword arguments:
=============== ===================================================
Keyword Description
=============== ===================================================
*patchlabel* label to be placed at the center of the diagram
Note: *label* (not *patchlabel*) will be passed to
the patch through ``**kwargs`` and can be used to
create an entry in the legend.
*flows* array of flow values
By convention, inputs are positive and outputs are
negative.
*orientations* list of orientations of the paths
Valid values are 1 (from/to the top), 0 (from/to
the left or right), or -1 (from/to the bottom). If
*orientations* == 0, inputs will break in from the
left and outputs will break away to the right.
*labels* list of specifications of the labels for the flows
Each value may be None (no labels), '' (just label
the quantities), or a labeling string. If a single
value is provided, it will be applied to all flows.
If an entry is a non-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* length between the bases of the input and output
groups
*pathlengths* list of lengths of the 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* index of the prior diagram to which this diagram
should be connected
*connect* 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* angle of rotation of the diagram [deg]
*rotation* is ignored if this diagram is connected
to an existing one (using *prior* and *connect*).
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).
=============== ===================================================
Valid kwargs are :meth:`matplotlib.patches.PathPatch` arguments:
%(Patch)s
As examples, ``fill=False`` and ``label='A legend entry'``.
By default, ``facecolor='#bfd1d4'`` (light blue) and
``linewidth=0.5``.
The indexing parameters (*prior* and *connect*) are zero-based.
The flows are placed along the top of the diagram from the inside out
in order of their index within the *flows* list or array. They are
placed along the sides of the diagram from the top down and along the
bottom from the outside in.
If the the sum of the inputs and outputs is nonzero, the discrepancy
will appear as a cubic Bezier curve along the top and bottom edges of
the trunk.
.. seealso::
:meth:`finish`
"""
# Check and preprocess the arguments.
if flows is None:
flows = np.array([1.0, -1.0])
else:
flows = np.array(flows)
n = flows.shape[0] # Number of flows
if rotation == None:
rotation = 0
else:
# In the code below, angles are expressed in deg/90
rotation /= 90.0
if orientations is None:
orientations = [0, 0]
assert len(orientations) == n, (
"orientations and flows must have the same length.\n"
"orientations has length %d, but flows has length %d."
% (len(orientations), n))
if labels != '' and getattr(labels, '__iter__', False):
# iterable() isn't used because it would give True if labels is a
# string
assert len(labels) == n, (
"If labels is a list, then labels and flows must have the "
"same length.\nlabels has length %d, but flows has length %d."
% (len(labels), n))
else:
labels = [labels]*n
assert trunklength >= 0, (
"trunklength is negative.\nThis isn't allowed, because it would "
"cause poor layout.")
if np.absolute(np.sum(flows)) > self.tolerance:
verbose.report(
"The sum of the flows is nonzero (%f).\nIs the "
"system not at steady state?" % np.sum(flows), 'helpful')
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 not (0.5 <= gain <= 2.0):
verbose.report(
"The scaled sum of the inputs is %f.\nThis may "
"cause poor layout.\nConsider changing the scale so"
" that the scaled sum is approximately 1.0." % gain, 'helpful')
if not (-2.0 <= loss <= -0.5):
verbose.report(
"The scaled sum of the outputs is %f.\nThis may "
"cause poor layout.\nConsider changing the scale so"
" that the scaled sum is approximately 1.0." % gain, 'helpful')
if prior is not None:
assert prior >= 0, "The index of the prior diagram is negative."
assert min(connect) >= 0, (
"At least one of the connection indices is negative.")
assert prior < len(self.diagrams), (
"The index of the prior diagram is %d, but there are "
"only %d other diagrams.\nThe index is zero-based."
% (prior, len(self.diagrams)))
assert connect[0] < len(self.diagrams[prior].flows), (
"The connection index to the source diagram is %d, but "
"that diagram has only %d flows.\nThe index is zero-based."
% (connect[0], len(self.diagrams[prior].flows)))
assert connect[1] < n, (
"The connection index to this diagram is %d, but this diagram"
"has only %d flows.\n The index is zero-based."
% (connect[1], n))
assert self.diagrams[prior].angles[connect[0]] is not None, (
"The connection cannot be made. Check that the magnitude "
"of flow %d of diagram %d is greater than or equal to the "
"specified tolerance." % (connect[0], prior))
flow_error = (self.diagrams[prior].flows[connect[0]] +
flows[connect[1]])
assert abs(flow_error) < self.tolerance, (
"The scaled sum of the connected flows is %f, which is not "
"within the tolerance (%f)." % (flow_error, 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:
verbose.report(
"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), 'helpful')
# 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 == 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:
assert orient == -1, (
"The value of orientations[%d] is %d, "
"but it must be -1, 0, or 1." % (i, orient))
if is_input:
angles[i] = UP
elif is_input == False:
angles[i] = DOWN
# Justify the lengths of the paths.
if iterable(pathlengths):
assert len(pathlengths) == n, (
"If pathlengths is a list, then pathlengths and flows must "
"have the same length.\npathlengths has length %d, but flows "
"has length %d." % (len(pathlengths), n))
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 not is_input:
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(zip(
angles, are_inputs, scaled_flows))):
if angle == UP and is_input:
pathlengths[n-i-1] = lllength
lllength += flow
elif angle == DOWN and not is_input:
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(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, zip(scaled_flows, pathlengths))):
if angle == RIGHT:
if not is_input:
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, 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 not is_input:
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(zip(
angles, are_inputs, zip(scaled_flows, pathlengths)))):
if angle == UP and is_input:
tips[n-i-1, :], label_locations[n-i-1, :] = self._add_input(
llpath, angle, *spec)
elif angle == DOWN and not is_input:
tips[n-i-1, :], label_locations[n-i-1, :] = self._add_output(
lrpath, angle, *spec)
# Add the left-side inputs from the bottom upwards.
has_left_input = False
for i, (angle, is_input, spec) in enumerate(reversed(zip(
angles, are_inputs, 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
tips[n-i-1, :], label_locations[n-i-1, :] = self._add_input(
llpath, angle, *spec)
# 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, zip(scaled_flows, pathlengths))):
if angle == RIGHT and not is_input:
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_point
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_point
tips = rotate(tips)
offset = self.diagrams[prior].tips[connect[0]] - tips[connect[1]]
translate = Affine2D().translate(*offset).transform_point
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 False: # Debug
print "llpath\n", llpath
print "ulpath\n", self._revert(ulpath)
print "urpath\n", urpath
print "lrpath\n", self._revert(lrpath)
xs, ys = zip(*vertices)
self.ax.plot(xs, ys, 'go-')
patch = PathPatch(Path(vertices, codes),
fc=kwargs.pop('fc', kwargs.pop('facecolor',
'#bfd1d4')), # Custom defaults
lw=kwargs.pop('lw', kwargs.pop('linewidth', 0.5)),
**kwargs)
self.ax.add_patch(patch)
# Add the path labels.
for i, (number, angle) in enumerate(zip(flows, angles)):
if labels[i] is None or angle is None:
labels[i] = ''
elif self.unit is not None:
quantity = self.format % abs(number) + self.unit
if labels[i] != '':
labels[i] += "\n"
labels[i] += quantity
texts = []
for i, (label, location) in enumerate(zip(labels, label_locations)):
if label:
s = label
else:
s = ''
texts.append(self.ax.text(x=location[0], y=location[1],
s=s,
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(Bunch(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).
Return value is a list of subdiagrams represented with the following
fields:
=============== ===================================================
Field Description
=============== ===================================================
*patch* Sankey outline (an instance of
:class:`~maplotlib.patches.PathPatch`)
*flows* values of the flows (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 will have an angle of 3
(DOWN), and an output from the top side will have
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* array in which each row is an [x, y] pair
indicating the positions of the tips (or "dips") of
the flow paths
If the magnitude of a flow is less the *tolerance*
for the instance of :class:`Sankey`, the flow is
skipped and its tip will be at the center of the
diagram.
*text* :class:`~matplotlib.text.Text` instance for the
label of the diagram
*texts* list of :class:`~matplotlib.text.Text` instances
for the labels of flows
=============== ===================================================
.. seealso::
:meth:`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
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.
Optional keyword arguments:
=============== ===================================================
Field Description
=============== ===================================================
*ax* axes onto which the data should be plotted
If *ax* isn't provided, new axes will be created.
*scale* 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* string representing the physical unit associated
with the flow quantities
If *unit* is None, then none of the quantities are
labeled.
*format* a Python number formatting string to be used in
labeling the flow as a quantity (i.e., a number
times a unit, where the unit is given)
*gap* space between paths that break in/break away
to/from the top or bottom
*radius* inner radius of the vertical paths
*shoulder* size of the shoulders of output arrowS
*offset* text offset (from the dip or tip of the arrow)
*head_angle* angle of the arrow heads (and negative of the angle
of the tails) [deg]
*margin* minimum space between Sankey outlines and the edge
of the plot area
*tolerance* acceptable maximum of the magnitude of the sum of
flows
The magnitude of the sum of connected flows cannot
be greater than *tolerance*.
=============== ===================================================
The optional arguments listed above are applied to all subdiagrams so
that there is consistent alignment and formatting.
If :class:`Sankey` is instantiated with any keyword arguments other
than those explicitly listed above (``**kwargs``), they will be passed
to :meth:`add`, which will create the first subdiagram.
In order to draw a complex Sankey diagram, create an instance of
:class:`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()
.. seealso::
:meth:`add`
:meth:`finish`
**Examples:**
.. plot:: mpl_examples/api/sankey_demo_basics.py
"""
# Check the arguments.
assert gap >= 0, (
"The gap is negative.\nThis isn't allowed because it "
"would cause the paths to overlap.")
assert radius <= gap, (
"The inner radius is greater than the path spacing.\n"
"This isn't allowed because it would cause the paths to overlap.")
assert head_angle >= 0, (
"The angle is negative.\nThis isn't allowed "
"because it would cause inputs to look like "
"outputs and vice versa.")
assert tolerance >= 0, (
"The tolerance is negative.\nIt 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)