matplotlib.sankey

Module for creating Sankey diagrams using Matplotlib.

class matplotlib.sankey.Sankey(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-06, **kwargs)

Bases: object

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)

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:

axAxes

Axes onto which the data should be plotted. If ax isn't provided, new Axes will be created.

scalefloat

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).

unitstr

The physical unit associated with the flow quantities. If unit is None, then none of the quantities are labeled.

formatstr 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.

gapfloat

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

radiusfloat

Inner radius of the vertical paths.

shoulderfloat

Size of the shoulders of output arrows.

offsetfloat

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

head_anglefloat

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

marginfloat

Minimum space between Sankey outlines and the edge of the plot area.

tolerancefloat

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

(Source code)

(2x.png, png)

(2x.png, png)

(2x.png, png)

add(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:

patchlabelstr

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.

flowslist 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.

orientationslist 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).

labelslist 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.

trunklengthfloat

Length between the bases of the input and output groups (in data-space units).

pathlengthslist 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.

priorint

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.

rotationfloat

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".

Property	Description
agg_filter	a filter function, which takes a (m, n, 3) float array and a dpi value, and returns a (m, n, 3) array and two offsets from the bottom left corner of the image
alpha	unknown
animated	bool
antialiased or aa	bool or None
capstyle	CapStyle or {'butt', 'projecting', 'round'}
clip_box	BboxBase or None
clip_on	bool
clip_path	Patch or (Path, Transform) or None
color	color
edgecolor or ec	color or None
facecolor or fc	color or None
figure	Figure or SubFigure
fill	bool
gid	str
hatch	{'/', '\', '|', '-', '+', 'x', 'o', 'O', '.', '*'}
hatch_linewidth	unknown
in_layout	bool
joinstyle	JoinStyle or {'miter', 'round', 'bevel'}
label	object
linestyle or ls	{'-', '--', '-.', ':', '', (offset, on-off-seq), ...}
linewidth or lw	float or None
mouseover	bool
path_effects	list of AbstractPathEffect
picker	None or bool or float or callable
rasterized	bool
sketch_params	(scale: float, length: float, randomness: float)
snap	bool or None
transform	Transform
url	str
visible	bool
zorder	float

See also

Sankey.finish

finish()

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 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