如何在 matplotlib 中设置纵横比? [英] How can I set the aspect ratio in matplotlib?

问题描述

我正在尝试制作方形图(使用 imshow)，即 1:1 的纵横比，但我不能.这些都不起作用:

I'm trying to make a square plot (using imshow), i.e. aspect ratio of 1:1, but I can't. None of these work:

import matplotlib.pyplot as plt

ax = fig.add_subplot(111,aspect='equal')
ax = fig.add_subplot(111,aspect=1.0)
ax.set_aspect('equal')
plt.axes().set_aspect('equal')

这些调用似乎只是被忽略了(我经常在使用 matplotlib 时遇到这个问题).

It seems like the calls are just being ignored (a problem I often seem to have with matplotlib).

推荐答案

魅力三倍.我的猜测是这是一个错误，Zhenya 的回答表明它已修复在最新版本中.我有 0.99.1.1 版，我创建了以下解决方案:

Third times the charm. My guess is that this is a bug and Zhenya's answer suggests it's fixed in the latest version. I have version 0.99.1.1 and I've created the following solution:

import matplotlib.pyplot as plt
import numpy as np

def forceAspect(ax,aspect=1):
    im = ax.get_images()
    extent =  im[0].get_extent()
    ax.set_aspect(abs((extent[1]-extent[0])/(extent[3]-extent[2]))/aspect)

data = np.random.rand(10,20)

fig = plt.figure()
ax = fig.add_subplot(111)
ax.imshow(data)
ax.set_xlabel('xlabel')
ax.set_aspect(2)
fig.savefig('equal.png')
ax.set_aspect('auto')
fig.savefig('auto.png')
forceAspect(ax,aspect=1)
fig.savefig('force.png')

这是force.png":

This is 'force.png':

以下是我失败的尝试，但希望能提供有用的信息.

Below are my unsuccessful, yet hopefully informative attempts.

第二个答案:

我在下面的原始答案"有点矫枉过正，因为它的作用类似于 axes.set_aspect().我认为您想使用 axes.set_aspect('auto').我不明白为什么会这样，但它为我生成了一个方形图像图，例如这个脚本:

My 'original answer' below is overkill, as it does something similar to axes.set_aspect(). I think you want to use axes.set_aspect('auto'). I don't understand why this is the case, but it produces a square image plot for me, for example this script:

import matplotlib.pyplot as plt
import numpy as np

data = np.random.rand(10,20)

fig = plt.figure()
ax = fig.add_subplot(111)
ax.imshow(data)
ax.set_aspect('equal')
fig.savefig('equal.png')
ax.set_aspect('auto')
fig.savefig('auto.png')

生成具有相等"纵横比的图像图:和一个具有自动"纵横比的:

Produces an image plot with 'equal' aspect ratio: and one with 'auto' aspect ratio:

下面在原始答案"中提供的代码为明确控制的纵横比提供了一个起点，但一旦调用 imshow 似乎就会被忽略.

The code provided below in the 'original answer' provides a starting off point for an explicitly controlled aspect ratio, but it seems to be ignored once an imshow is called.

原始答案:

以下是一个例程示例，该例程将调整子图参数以便您获得所需的纵横比:

Here's an example of a routine that will adjust the subplot parameters so that you get the desired aspect ratio:

import matplotlib.pyplot as plt

def adjustFigAspect(fig,aspect=1):
    '''
    Adjust the subplot parameters so that the figure has the correct
    aspect ratio.
    '''
    xsize,ysize = fig.get_size_inches()
    minsize = min(xsize,ysize)
    xlim = .4*minsize/xsize
    ylim = .4*minsize/ysize
    if aspect < 1:
        xlim *= aspect
    else:
        ylim /= aspect
    fig.subplots_adjust(left=.5-xlim,
                        right=.5+xlim,
                        bottom=.5-ylim,
                        top=.5+ylim)

fig = plt.figure()
adjustFigAspect(fig,aspect=.5)
ax = fig.add_subplot(111)
ax.plot(range(10),range(10))

fig.savefig('axAspect.png')

这会产生一个像这样的图:

This produces a figure like so:

我可以想象，如果您在图中有多个子图，您可能希望将 y 和 x 子图的数量作为关键字参数(每个默认为 1)包含在所提供的例程中.然后使用这些数字和 hspace 和 wspace 关键字，您可以使所有子图具有正确的纵横比.

I can imagine if your having multiple subplots within the figure, you would want to include the number of y and x subplots as keyword parameters (defaulting to 1 each) to the routine provided. Then using those numbers and the hspace and wspace keywords, you can make all the subplots have the correct aspect ratio.

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