Hi List,
I made a script to draw very simple (single-direction single-input
single-sided single-everything) Sankey diagrams (attached). I think I
could share, if it can be of any use...
Cheers,
Yannick
#!/usr/bin/env python
# Time-stamp: <2010-02-10 01:49:08 ycopin>
import numpy as N
import matplotlib.pyplot as P
import matplotlib.patches as mpatches
from matplotlib.path import Path
def sankey(ax, losses, labels=None,
dx=40, dy=10, angle=45, w=3, dip=10, offset=2, **kwargs):
"""Draw a Sankey diagram.
losses: array of losses, should sum up to 100%
labels: loss labels (same length as losses),
or None (use default labels) or '' (no labels)
dx: horizontal elongation
dy: vertical elongation
angle: arrow angle [deg]
w: arrow shoulder
dip: input dip
offset: text offset
**kwargs: propagated to Patch (e.g. fill=False)
Return (patch,texts)."""
assert sum(losses)==100, "Input losses don't sum up to 100%"
def add_loss(loss, last=False):
h = (loss/2+w)*N.tan(angle/180.*N.pi) # Arrow tip height
move,(x,y) = path[-1] # Use last point as reference
if last: # Final loss (horizontal)
path.extend([(Path.LINETO,[x+dx,y]),
(Path.LINETO,[x+dx,y+w]),
(Path.LINETO,[x+dx+h,y-loss/2]), # Tip
(Path.LINETO,[x+dx,y-loss-w]),
(Path.LINETO,[x+dx,y-loss])])
tips.append(path[-3][1])
else: # Intermediate loss (vertical)
path.extend([(Path.LINETO,[x+dx/2,y]),
(Path.CURVE3,[x+dx,y]),
(Path.CURVE3,[x+dx,y+dy]),
(Path.LINETO,[x+dx-w,y+dy]),
(Path.LINETO,[x+dx+loss/2,y+dy+h]), # Tip
(Path.LINETO,[x+dx+loss+w,y+dy]),
(Path.LINETO,[x+dx+loss,y+dy]),
(Path.CURVE3,[x+dx+loss,y-loss]),
(Path.CURVE3,[x+dx/2+loss,y-loss])])
tips.append(path[-5][1])
tips = [] # Arrow tip positions
path = [(Path.MOVETO,[0,100])] # 1st point
for i,loss in enumerate(losses):
add_loss(loss, last=(i==(len(losses)-1)))
path.extend([(Path.LINETO,[0,0]),
(Path.LINETO,[dip,50]), # Dip
(Path.CLOSEPOLY,[0,100])])
codes,verts = zip(*path)
verts = N.array(verts)
# Path patch
path = Path(verts,codes)
patch = mpatches.PathPatch(path, **kwargs)
ax.add_patch(patch)
# Labels
if labels=='': # No labels
pass
elif labels is None: # Default labels
labels = [ '%2d%%' % loss for loss in losses ]
else:
assert len(labels)==len(losses)
texts = []
for i,label in enumerate(labels):
x,y = tips[i] # Label position
last = (i==(len(losses)-1))
if last:
t = ax.text(x+offset,y,label, ha='left', va='center')
else:
t = ax.text(x,y+offset,label, ha='center', va='bottom')
texts.append(t)
# Axes management
ax.set_xlim(verts[:,0].min()-10, verts[:,0].max()+40)
ax.set_ylim(verts[:,1].min()-10, verts[:,1].max()+20)
ax.set_aspect('equal', adjustable='datalim')
ax.set_xticks([])
ax.set_yticks([])
return patch,texts
if __name__=='__main__':
losses = [10.,20.,5.,15.,10.,40.]
labels = ['First','Second','Third','Fourth','Fifth','Hurray!']
labels = [ s+'\n%d%%' % l for l,s in zip(losses,labels) ]
fig = P.figure()
ax = fig.add_subplot(1,1,1)
patch,texts = sankey(ax, losses, labels, fc='g', alpha=0.2)
texts[1].set_color('r')
texts[-1].set_fontweight('bold')
P.show()
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