matplotlib: axes border and tick mark/label locations

Question

The end result I'm attempting to achieve is to have a "thicker" black boarder around my plot, along xmin, xmax, ymin, & ymax. I've tried a couple of different things (such as just drawing a rectangle on the plot, see below), but I have not been able to achieve the desired results for a few reasons.

Because I cannot just use the spines (I've set 2 of them to always be at 0), I need to add some other line or rectangle to create the desired border.

By default the first and last tick labels overhang the axes. I "overcame" this by changing the horizontal or vertical alignment, but they could still use some more padding. I know this is possible, but requires a transform and is a bit clunky.

Now I'd like to remove the first and last tick marks on both axis. This is because given the way the rectangle is drawn it is always inside the plot area, but the first and last tick mark are always outside it, regardless of how thick the rectangle is. Making the rectangle thicker only causes it to overlap the first and last tick label more, which the actual tick mark remains outside the rectangle.

Any other suggestions on how to achieve this kind of border while always maintaining an axis at 0, 0 would be welcomed. That is the overall desired result.

import numpy as np
import matplotlib.pyplot as plt
import matplotlib
from matplotlib.patches import Rectangle

X = np.random.randint(low=-9, high=9, size=10)
Y = np.random.randint(low=-9, high=9, size=10)

fig, ax = plt.subplots()
ax.axis([-10, 10, -10, 10])
ax.spines['left'].set_position('zero')
ax.spines['bottom'].set_position('zero')
ax.spines['top'].set_visible(False)
ax.spines['right'].set_visible(False)
plt.setp(ax.xaxis.get_majorticklabels()[0], ha='left')
plt.setp(ax.xaxis.get_majorticklabels()[-1], ha='right')
plt.setp(ax.yaxis.get_majorticklabels()[0], va='bottom')
plt.setp(ax.yaxis.get_majorticklabels()[-1], va='top')
patPlotBorder = ax.add_artist(Rectangle((-10, -10), 20, 20, fill=False, color='k', linewidth=2))
ax.grid(True)
fig.set_tight_layout(True)
ax.scatter(X, Y, c="b", marker="o", s=40)
plt.show()

ImportanceOfBeingErnest ImportanceOfBeingErnest · Accepted Answer · 2018-12-20T16:27:05

Without changing much of your code, you can set the clip_on to False, such that the complete rectangle is shown.

border = Rectangle((-10, -10), 20, 20, fill=False, color='k', linewidth=3, clip_on=False)
ax.add_artist(border)

Since the gridlines are shown above the axes content, you have some grey line within the rectangle border.

Alternatively, you can use two axes. One with all the content and the modified spine positions etc., and one where you just make the spines bold and remove all the rest.

import numpy as np
import matplotlib.pyplot as plt

X = np.random.randint(low=-9, high=9, size=10)
Y = np.random.randint(low=-9, high=9, size=10)

fig, ax = plt.subplots()
ax2 = fig.add_subplot(111)
ax2.patch.set_visible(False)
ax2.tick_params(left=False, bottom=False, labelleft=False, labelbottom=False)
for _, sp in ax2.spines.items():
    sp.set_linewidth(3)

ax.axis([-10, 10, -10, 10])
ax.spines['left'].set_position('zero')
ax.spines['bottom'].set_position('zero')
ax.spines['top'].set_visible(False)
ax.spines['right'].set_visible(False)
plt.setp(ax.xaxis.get_majorticklabels()[0], ha='left')
plt.setp(ax.xaxis.get_majorticklabels()[-1], ha='right')
plt.setp(ax.yaxis.get_majorticklabels()[0], va='bottom')
plt.setp(ax.yaxis.get_majorticklabels()[-1], va='top')

ax.grid(True)
fig.set_tight_layout(True)
ax.scatter(X, Y, c="b", marker="o", s=40)
plt.show()

matplotlib: axes border and tick mark/label locations

2 Answers