set matplotlib 3d plot aspect ratio

import matplotlib.pyplot as plt
from mpl_toolkits.mplot3d import Axes3D

Setting the aspect ratio works for 2d plots:

ax = plt.axes()
ax.plot([0,1],[0,10])
ax.set_aspect('equal','box')

But does not for 3d:

ax = plt.axes(projection='3d')
ax.plot([0,1],[0,1],[0,10])
ax.set_aspect('equal','box')

Is there a different syntax for the 3d case, or it’s not implemented?

Answers:

Thank you for visiting the Q&A section on Magenaut. Please note that all the answers may not help you solve the issue immediately. So please treat them as advisements. If you found the post helpful (or not), leave a comment & I’ll get back to you as soon as possible.

Method 1

As of matplotlib 3.3.0, Axes3D.set_box_aspect seems to be the recommended approach.

import numpy as np
import matplotlib.pyplot as plt

xs, ys, zs = ...
ax = plt.axes(projection='3d')

ax.set_box_aspect((np.ptp(xs), np.ptp(ys), np.ptp(zs)))  # aspect ratio is 1:1:1 in data space

ax.plot(xs, ys, zs)

Method 2

I didn’t try all of these answers, but this kludge did it for me:

def axisEqual3D(ax):
    extents = np.array([getattr(ax, 'get_{}lim'.format(dim))() for dim in 'xyz'])
    sz = extents[:,1] - extents[:,0]
    centers = np.mean(extents, axis=1)
    maxsize = max(abs(sz))
    r = maxsize/2
    for ctr, dim in zip(centers, 'xyz'):
        getattr(ax, 'set_{}lim'.format(dim))(ctr - r, ctr + r)

Method 3

Looks like this feature has since been added so thought I’d add an answer for people who come by this thread in the future like I did:

fig = plt.figure(figsize=plt.figaspect(0.5)*1.5) #Adjusts the aspect ratio and enlarges the figure (text does not enlarge)
ax = fig.add_subplot(projection='3d')

figaspect(0.5) makes the figure twice as wide as it is tall. Then the *1.5 increases the size of the figure. The labels etc won’t increase so this is a way to make the graph look less cluttered by the labels.

Method 4

If you know the bounds, eg. +-3 centered around (0,0,0), you can add invisible points like this:

import numpy as np
import pylab as pl
from mpl_toolkits.mplot3d import Axes3D
fig = pl.figure()
ax = fig.add_subplot(projection='3d')
ax.set_aspect('equal')
MAX = 3
for direction in (-1, 1):
    for point in np.diag(direction * MAX * np.array([1,1,1])):
        ax.plot([point[0]], [point[1]], [point[2]], 'w')

Method 5

I think setting the correct “box aspect” is a good solution:

ax.set_box_aspect(aspect = (1,1,1))

import matplotlib.pyplot as plt

fig = plt.figure()
ax = fig.add_subplot(projection='3d')
ax.set_box_aspect(aspect = (1,1,1))

ax.plot(dataX,dataY,dataZ)

https://matplotlib.org/stable/api/_as_gen/mpl_toolkits.mplot3d.axes3d.Axes3D.html?highlight=3d%20set_box_aspect#mpl_toolkits.mplot3d.axes3d.Axes3D.set_box_aspect

Method 6

If you know the bounds you can also set the aspect ratio this way:

ax.auto_scale_xyz([minbound, maxbound], [minbound, maxbound], [minbound, maxbound])

Method 7

My understanding is basically that this isn’t implemented yet (see this bug in GitHub). I’m also hoping that it is implemented soon. See This link for a possible solution (I haven’t tested it myself).

Method 8

Another helpful (hopefully) solution when, for example, it is necessary to update an already existing figure:

world_limits = ax.get_w_lims()
ax.set_box_aspect((world_limits[1]-world_limits[0],world_limits[3]-world_limits[2],world_limits[5]-world_limits[4]))

get_w_lims()

set_box_aspect()

Method 9

A follow-up to Matt Panzer’s answer.

limits = np.array([getattr(ax, f'get_{axis}lim')() for axis in 'xyz'])
ax.set_box_aspect(np.ptp(limits, axis=1))

This may soon become unneccessary, since there is a pull request underway to make ax.set_aspect('equal') work.

Method 10

I tried several methods, such as ax.set_box_aspect(aspect = (1,1,1)) and it does not work. I want a sphere to show up as a sphere — not ellipsoid. I wrote this function and tried it on a variety of data. It is a hack and it is not perfect, but pretty close.

def set_aspect_equal(ax):
    """ 
    Fix the 3D graph to have similar scale on all the axes.
    Call this after you do all the plot3D, but before show
    """
    X = ax.get_xlim3d()
    Y = ax.get_ylim3d()
    Z = ax.get_zlim3d()
    a = [X[1]-X[0],Y[1]-Y[0],Z[1]-Z[0]]
    b = np.amax(a)
    ax.set_xlim3d(X[0]-(b-a[0])/2,X[1]+(b-a[0])/2)
    ax.set_ylim3d(Y[0]-(b-a[1])/2,Y[1]+(b-a[1])/2)
    ax.set_zlim3d(Z[0]-(b-a[2])/2,Z[1]+(b-a[2])/2)
    ax.set_box_aspect(aspect = (1,1,1))

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0