make axes the same length in matplotlib pyplot

Question

I want to make square independent from the axis units. I know I can set the figure dimensions equal with figure(figsize=(10, 10)) for example, and I can set the axis scale ratio equal with set_aspect('equal'), but how can I force the actual axis length to be equal, e.g., make xaxis and yaxis each 10 inches long?

EDIT Example code

import matplotlib.pyplot as plt
import matplotlib.gridspec as gridspec
from matplotlib.ticker import MaxNLocator
import numpy as np

x1 = 1
y1 = [10., 1000.]
err1 = 0.00865
x2 = 2
y2 = [9., 900.]
err2 = 0.00658

len_xaxis,len_yaxis = 5.,5. #fix here your numbers
xspace, yspace = .9, .9 # change the size of the void border here.
x_fig,y_fig = len_xaxis / xspace, len_yaxis / yspace

for i in range(2):
    plt.clf()
    #    fig = plt.figure(figsize=(6, 6))
    fig = plt.figure(figsize=(x_fig,y_fig))
    plt.subplots_adjust(left=1-xspace, right = xspace, top=yspace, bottom = 1-yspace)
    gs = gridspec.GridSpec(3, 1)
    gs.update(hspace=0., wspace=0.)
    ax1 = plt.subplot(gs[0:2, 0])

    ax1.errorbar(x1, y1[i], yerr=err1)
    ax1.errorbar(x2, y2[i], yerr=err2)

    ax1.invert_yaxis()

    plt.setp(ax1.get_xticklabels(), visible=False)  # Remove x-labels between the plots
    plt.xlim(0, 3)

    ax2 = plt.subplot(gs[2, 0], sharex=ax1)

    nbins = len(ax1.get_yticklabels())
    ax1.yaxis.set_major_locator(MaxNLocator(nbins=8, prune='both'))
    nbins = len(ax2.get_yticklabels())
    ax2.yaxis.set_major_locator(MaxNLocator(nbins=6, prune='both'))

    plt.tight_layout()
    plt.savefig('prune_%d.png' % i)
    plt.close()

gg349 · Accepted Answer · 2015-01-13 22:04:25Z

2

Play with the plt.subplots_adjust() function. Example for 5 inches instead of 10:

len_xaxis,len_yaxis = 5.,5. #fix here your numbers

xspace, yspace = .9, .9 # change the size of the void border here.

x_fig,y_fig = len_xaxis / xspace, len_yaxis / yspace
figure(figsize=(x_fig,y_fig))
plt.subplots_adjust(left=1-xspace, right = xspace, top=yspace, bottom = 1-yspace)
plot([1,2,3],[-1,3,5])

answered Jan 13, 2015 at 22:04

gg349

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6 Comments

frixhax Over a year ago

Well, that does not work. Depending on the data (and therefore opn the length of the axis labels) in different plots I get the same hight in all plots but not the same width. The x and y axis don't have a fix inch length ratio.

frixhax Over a year ago

I tried your code with the example I postet here. Depending on what y-values I use (i.e., how many digits the y tick labels have) the axis length ratio changes, also with your code added.

gg349 Over a year ago

This is not an example to work on. I had a look at that code, and the solution worked, the 2 axes (top and bottom) together occupy exactly 5x5 inches. Please edit the question with an example of it failing.

frixhax Over a year ago

Thanks, I included an example already with your suggestion in it. You are right, your code works. However, I use plt.tight_layout(), which seems to override the adjustment and I get differing axis length ratios in the two plots. Is there a way to circumvent that?

gg349 Over a year ago

Not that i am award of. Basically that command changes the same parameters of plt.subplots_adjust() overriding it

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