Matplotlib multiple grids zorder not working with errorbars

Question

I am currently dealing with some strange behavior of matplotlib when plotting multiple errorbars with different y axes into one subplot.

When doing so, the grid corresponding to the second errorbar plot always overlaps the first errorbar plot. With the zorder options I was only able to move the other grid below the errorbars.

I would like both grids to be below the two errorbars. Does anyone know a solution to this, or is this a bug in matplotlib?

I am using Python 2.7.12 with matplotlib 1.5.1.

Minimal working example:

import numpy as np
import matplotlib
matplotlib.use('Agg')
import matplotlib.pyplot as plt
import matplotlib.colors as colors

# numbers of epochs
ttimes_means_list = [251.4, 153.3, 22.0, 202.1, 46.6]
ttimes_stddevs_list = [32.1, 35.1, 12.0, 84.9, 14.7]
# numbers of times
times_means_list = [5231, 3167, 860, 3932, 1244]
times_stddevs_list = [1381, 572, 253, 1445, 215]

labels = ['x1', 'x2', 'x3', 'x4', 'x5']
linewidth=3

xvalues = np.arange(0, len(times_means_list), 1)
xvalues_s = xvalues + 0.1

fig = plt.figure()
ax1 = fig.add_subplot(111)
ax2 = ax1.twinx()
ax1.set_ylabel('Number')
ax1.xaxis.grid(False)
ax1.yaxis.grid(True, color='navy', linewidth=linewidth/2.0)
ax2.xaxis.grid(False)
ax1.set_zorder(0)
ax2.set_zorder(0)
ax2.yaxis.grid(True, color='darkorange', linewidth=linewidth/2.0)
ax2.set_ylabel('Time')
ax1.set_xticks(xvalues)
ax2.set_xticks(xvalues)
ax1.set_xticklabels(labels)
ax2.set_xticklabels(labels)
ax1.set_xlabel('x label')
errplot1 = ax1.errorbar(xvalues, ttimes_means_list, yerr=ttimes_stddevs_list,
        linestyle="None", elinewidth=linewidth, color='navy', label='Number',
        capthick=linewidth, zorder=10)
errplot2 = ax2.errorbar(xvalues_s, times_means_list, yerr=times_stddevs_list, 
        linestyle="None", elinewidth=linewidth, color='darkorange',
        label='Time', capthick=linewidth, zorder=10)
ax1.set_axisbelow(True)
ax2.set_axisbelow(True)
fig.legend((errplot1, errplot2), ('number', 'time'), 
        loc='upper right', numpoints=1)
plt.xlim(-0.5, len(times_means_list)-0.5)
plt.title('Some plot title')
plt.savefig('mwe_plot.pdf')
plt.clf()

Output plot (the orange grid dots are overlapping the blue bars): Multiple errorbars with multiple grids

hxysayhi hxysayhi · Accepted Answer · 2017-04-11T09:10:00

Maybe you can draw the 'navy' line twice.

import numpy as np
import matplotlib
matplotlib.use('Agg')
import matplotlib.pyplot as plt
import matplotlib.colors as colors

# numbers of epochs
ttimes_means_list = [251.4, 153.3, 22.0, 202.1, 46.6]
ttimes_stddevs_list = [32.1, 35.1, 12.0, 84.9, 14.7]
# numbers of times
times_means_list = [5231, 3167, 860, 3932, 1244]
times_stddevs_list = [1381, 572, 253, 1445, 215]

labels = ['x1', 'x2', 'x3', 'x4', 'x5']
linewidth=3

xvalues = np.arange(0, len(times_means_list), 1)
xvalues_s = xvalues + 0.1

fig = plt.figure()
ax1 = fig.add_subplot(111)
ax2 = ax1.twinx()
ax1.set_ylabel('Number')
ax1.xaxis.grid(False)
g1 = ax1.yaxis.grid(True, color='navy', linewidth=linewidth/2.0)
ax2.xaxis.grid(False)
ax1.set_zorder(0)
ax2.set_zorder(0)
g2 = ax2.yaxis.grid(True, color='darkorange', linewidth=linewidth/2.0)
ax2.set_ylabel('Time')
ax1.set_xticks(xvalues)
ax2.set_xticks(xvalues)
ax1.set_xticklabels(labels)
ax2.set_xticklabels(labels)
ax1.set_xlabel('x label')
ax1.errorbar(xvalues, ttimes_means_list, yerr=ttimes_stddevs_list,
        linestyle="None", elinewidth=1, color='navy', label='Number',
        capthick=1, zorder=10,)
errplot2 = ax2.errorbar(xvalues_s, times_means_list, yerr=times_stddevs_list, 
        linestyle="None", elinewidth=linewidth, color='darkorange',
        label='Time', capthick=linewidth, zorder=10)
ax1.set_axisbelow(True)
ax2.set_axisbelow(True)

# draw the 'navy' line again
ax3 = ax1.twinx()
ax3.yaxis.grid(False)
errplot1 = ax3.errorbar(xvalues, ttimes_means_list, yerr=ttimes_stddevs_list,
        linestyle="None", elinewidth=linewidth, color='navy', label='Number',
        capthick=linewidth, zorder=10)

fig.legend((errplot1, errplot2), ('number', 'time'), 
        loc='upper right', numpoints=1)
plt.xlim(-0.5, len(times_means_list)-0.5)
plt.title('Some plot title')
# plt.savefig('mwe_plot.pdf')
# plt.clf()

plt.show()

And you will get:

Matplotlib multiple grids zorder not working with errorbars

1 Answers