Bug in mplot3D with PolyCollection: (0, 0) data point is always inserted into the data set.

[danieljfarrell]

This a a bug related to stacked xy-plots example,
http://matplotlib.org/examples/mplot3d/polys3d_demo.html

matplotlib seems to be inserting a vertex at (0,0) into the data set.

• Is there a different way to plot stacked xy-plots that avoids this bug?
• Maybe the fix is fairly simple, if all that is happening is that an additional vertex is getting inserted?

The following example is based on the poly3d_demo script linked above. If we change the data set so that the data doesn't include a point at x=0, for example change line 12 from,

xs = np.arange(0, 10, 0.4)

to,

xs = np.arange(5, 10, 0.4)

A erroneous line is drawn from the data set to the (0,0) point.

The following script produces the result(s) below, using matplotlib 1.3.0.

Example 1

When the x-axis is changed to only include the range of the data set the result look even worse,

Example 2

from mpl_toolkits.mplot3d import Axes3D
from matplotlib.collections import PolyCollection
from matplotlib.colors import colorConverter
import matplotlib.pyplot as plt
import numpy as np

fig = plt.figure()
ax = fig.gca(projection='3d')

cc = lambda arg: colorConverter.to_rgba(arg, alpha=0.6)

xs = np.arange(5, 10, 0.4) # The data x-range has been changed to run between 5--10
verts = []
zs = [0.0, 1.0, 2.0, 3.0]
for z in zs:
    ys = np.random.rand(len(xs))
    ys[0], ys[-1] = 0, 0
    verts.append(list(zip(xs, ys)))

poly = PolyCollection(verts, facecolors = [cc('r'), cc('g'), cc('b'),
                                           cc('y')])
poly.set_alpha(0.7)
ax.add_collection3d(poly, zs=zs, zdir='y')

ax.set_xlabel('X')
ax.set_xlim3d(5, 10) # This has been changed to 5 to adjust the axis range to the data
ax.set_ylabel('Y')
ax.set_ylim3d(-1, 4)
ax.set_zlabel('Z')
ax.set_zlim3d(0, 1)

plt.show()

[mdboom]

@WeatherGod: any thoughts?

[tacaswell]

related to http://stackoverflow.com/questions/16305256/couldnt-remove-origin-point-in-matplotlib-polycollection which generated issue #2045

[tacaswell]

closed by #3239