Matplotlib add_subplot & change_geometry bug?

Question

I am building a PyQt4 GUI with embedded Matplotlib (1.4.3). It lets a user select from a list of available parameters to plot & gives them control to add/remove, rescale subplots etc. to send their data to. Anyway, I came across this behavior of add_subplot followed by change_geometry that I didn't expect.

Make a subplot in the 2,1,2 position:

import numpy as np
import matplotlib.pyplot as plt

x = np.arange(0, 10, 0.1)
y1 = 0.05 * x**2
y2 = -1 *y1
figure = plt.figure()
ax1 = figure.add_subplot(2,1,2,label='sub2')
ax1.plot(x, y1, 'g-')
plt.show()

That was a mistake lets change it to subplot #1 and relabel

ax1.change_geometry(2,1,1)
ax1.set_label('sub1')

Ok, Now lets add subplot 2 for real this time...

ax2 = figure.add_subplot(2,1,2,label='sub2')
ax2.plot(x, y2, 'b-')
plt.draw()

Wait a minute it plotted on Subplot 1 ... and where is my subplot 2? Lets look at ax1, and ax2

ax1
<matplotlib.axes._subplots.AxesSubplot at 0xcaa32b0>
ax2
<matplotlib.axes._subplots.AxesSubplot at 0xcaa32b0>

They are the same axes? So after some digging I came across This GitHub Issue 429 and it says it is fixed ... but it doesn't look like it to me. Am I missing something or is this really still an issue?

What version of matplotlib are you using? Your example works fine for me in 1.4.3 — Ajean
– Ajean, Commented Jul 24, 2015 at 15:23
As stated above I am using 1.4.3. So at the end you have 2 separate subplots? I have tired it on 2 different machines (one with 1.4.3 and one with 1.4.2) both in an Ipython console & regular Python3 (using anaconda) and I get the results shown in the picture above ... strange. — Aero Engy
– Aero Engy, Commented Jul 24, 2015 at 15:56
Ah, sorry, I just missed the version in the question. Yes, I get two separate subplots when I try it. Hmm. Are you doing it interactively or in a script? — Ajean
– Ajean, Commented Jul 24, 2015 at 16:04
Ok, well, you are right, this is strange. When I put the whole code into a single cell I duplicate your results. When I first tried it I just typed things into ipython one line at a time and it worked fine. Hmmm.... — Ajean
– Ajean, Commented Jul 24, 2015 at 16:12
My original issue was in a PyQT4 GUI application were the user can manipulate/move/add subplots. Occasionally with the right steps of add/remove etc. I would get a line plotted on the wrong axes and a missing subplot. The full application was to long to post here so I cut it down to a small example to demonstrate the issue. The only real difference in my PyQT app is that I don't use matplotlib.pyplot instead I import Figure and FigureCanvasQTAgg ... but the behavior is the same either way. — Aero Engy
– Aero Engy, Commented Jul 24, 2015 at 17:18

Aero Engy · Accepted Answer · 2015-07-25 14:10:06Z

1

I create this as an issue on Github. It was confirmed and added to the next point release milestone.

GitHub Issue 4786

answered Jul 25, 2015 at 14:10

Aero Engy

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