具有两个尺度共享原点的 Matplotlib 轴 [英] Matplotlib axis with two scales shared origin

问题描述

我需要在 Matplotlib 中用不同的 Y 轴比例覆盖两个数据集.数据包含正值和负值.我希望两个轴共享一个原点，但 Matplotlib 默认不对齐两个比例.

I need two overlay two datasets with different Y-axis scales in Matplotlib. The data contains both positive and negative values. I want the two axes to share one origin, but Matplotlib does not align the two scales by default.

import numpy as np
import matplotlib.pyplot as plt

fig = plt.figure()
ax1 = fig.add_subplot(111)
ax2 = ax1.twinx()

ax1.bar(range(6), (2, -2, 1, 0, 0, 0))
ax2.plot(range(6), (0, 2, 8, -2, 0, 0))
plt.show()

我想可以用 .get_ylim() 和 .set_ylim() 执行一些计算，两个对齐两个比例.有没有更简单的解决方案?

I suppose it is possible to perform some computation with .get_ylim() and .set_ylim() two align the two scales. Is there an easier solution?

推荐答案

使用 align_yaxis() 函数:

use the align_yaxis() function:

import numpy as np
import matplotlib.pyplot as plt

def align_yaxis(ax1, v1, ax2, v2):
    """adjust ax2 ylimit so that v2 in ax2 is aligned to v1 in ax1"""
    _, y1 = ax1.transData.transform((0, v1))
    _, y2 = ax2.transData.transform((0, v2))
    inv = ax2.transData.inverted()
    _, dy = inv.transform((0, 0)) - inv.transform((0, y1-y2))
    miny, maxy = ax2.get_ylim()
    ax2.set_ylim(miny+dy, maxy+dy)


fig = plt.figure()
ax1 = fig.add_subplot(111)
ax2 = ax1.twinx()

ax1.bar(range(6), (2, -2, 1, 0, 0, 0))
ax2.plot(range(6), (0, 2, 8, -2, 0, 0))

align_yaxis(ax1, 0, ax2, 0)
plt.show()

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