Matplotlib：扩展轴以填充图形，x 和 y 的比例相同

Question

I know 2 things but separately.

figure.tight_layout 

will expand my current axes

axes.aspect('equal')

will keep same scale on x and y.

But when I use them both I get square axes view and I want it to be expanded. By keeping same scale I mean there is same distance from 0 to 1 on x and y axis. Is there any way to make it happen? Keep same scale and expand to full figure(not only a square) The answer should work with autoscale

Answer 1

There might be less clumsy way, but at least you can do it manually. A very simple example:

import matplotlib.pyplot as plt

fig = plt.figure()
ax = fig.add_subplot(111)
ax.plot([0,1],[1,0])
ax.set_aspect(1)
ax.set_xlim(0, 1.5)

creates

which honours the aspect ratio.

If you want to have the automatic scaling offered by the tight_layout , then you'll have to do some maths of your own:

import matplotlib.pyplot as plt

fig = plt.figure()
ax = fig.add_subplot(111)
ax.plot([0,1],[1,0])
fig.tight_layout()

# capture the axis positioning in pixels
bb = fig.transFigure.transform(ax.get_position())
x0, y0 = bb[0]
x1, y1 = bb[1]
width = x1 - x0
height = y1 - y0

# set the aspect ratio 
ax.set_aspect(1)

# calculate the aspect ratio of the plot
plot_aspect = width / height

# get the axis limits in data coordinates
ax0, ax1 = ax.get_xlim()
ay0, ay1 = ax.get_ylim()
awidth = ax1 - ax0
aheight = ay1 - ay0

# calculate the plot aspect
data_aspect = awidth / aheight

# check which one needs to be corrected
if data_aspect < plot_aspect:
    ax.set_xlim(ax0, ax0 + plot_aspect * aheight)
else:
    ax.set_ylim(ay0, ay0 + awidth / plot_aspect)

Of course, you may set the xlim and ylim any way you want, you might, for example, want to add an equal amount of space to either end of the scale.

Answer 2

The solution that worked in my case was to call

axis.aspect("equal")
axis.set_adjustable("datalim")

stolen from this example in the documentation.