CODEWITHSUNDEEP
pythonmatplotlib
DanHickstein
DanHickstein

Reputation: 6938

Automatically make matplotlib axes square and equal xlim and ylim

Let's say that I want to plot an ellipse in matplotlib:

import numpy as np
import matplotlib.pyplot as plt

x =   np.sin(np.linspace(0,2*np.pi,100))
y = 2*np.cos(np.linspace(0,2*np.pi,100))

ax = plt.subplot(111)
ax.plot(x,y)
plt.show()

The result looks like a circle: enter image description here

I can get the result that I want by adding five lines of code:

import numpy as np
import matplotlib.pyplot as plt

x =   np.sin(np.linspace(0,2*np.pi,100))
y = 2*np.cos(np.linspace(0,2*np.pi,100))

ax = plt.subplot(111)
ax.plot(x,y)

#make the axes square and equal
ax.set_aspect('equal')

minimum = np.min((ax.get_xlim(),ax.get_ylim()))
maximum = np.max((ax.get_xlim(),ax.get_ylim()))

ax.set_xlim(minimum*1.2,maximum*1.2)
ax.set_ylim(minimum*1.2,maximum*1.2)

plt.show()

enter image description here

But this seems very clunky. Is there a function built into matplotlib to give the expected behavior automagically?

Upvotes: 3

Views: 5210

Answers (2)

fizcris
fizcris

Reputation: 63

If it is of any use, here is the similar code for MATLAB:

% Make axes equal in size and lenght
% ax3 is an axe() object.
    axis (ax3,'auto')
    axis (ax3,'square')
    minimum = min(abs([ax3.XLim,ax3.YLim]));
    maximum = max(abs([ax3.XLim,ax3.YLim]));
    limit = max(minimum,maximum);
    limit = round(limit,0);
    axis(ax3,[-limit limit -limit limit]);

    ticks = [-limit:limit/5:limit];
    xticks(ax3, ticks);
    yticks(ax3,ticks);
    grid(ax3,'on')

Upvotes: 0

Janion
Janion

Reputation: 118

A quick google threw this up: http://matplotlib.org/examples/pylab_examples/equal_aspect_ratio.html. I haven't tested it myself, though. 

ax.set_aspect('equal', 'datalim')
ax.margins(0.1)

Upvotes: 5

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