我创建了一种方法来对齐多个y轴的刻度(可能超过2个),即使不同轴上的比例也可能不同。
下面是一个示例图:
![enter image description here](https://istack.dev59.com/xRxpn.webp)
这里有3个y轴,一个在左侧是蓝色,另外两个在右侧一个是绿色一个是红色。三条曲线分别用相应的颜色绘制到y轴上。请注意它们具有非常不同的数量级。
- 左边的图:没有对齐。
- 中间的图:在每个y轴的(大约)下限处对齐。
- 右边的图:在指定的值上对齐:
0
为蓝色,
2.2*1e8
为红色,
44
为绿色。这些是任意选择的。
我的做法是将每个y数组缩放至1-100的范围内,然后将所有缩放后的y值合并成单个数组,从中使用
MaxNLocator
创建一组新的刻度。 然后使用相应的缩放因子将此新的刻度重新缩放以获得每个轴的新刻度。 如果需要特定的对齐,则在缩放之前移动y数组,然后在缩放后移回来。
完整代码在这里(关键函数是
alignYaxes()
):
import matplotlib.pyplot as plt
import numpy as np
def make_patch_spines_invisible(ax):
'''Used for creating a 2nd twin-x axis on the right/left
E.g.
fig, ax=plt.subplots()
ax.plot(x, y)
tax1=ax.twinx()
tax1.plot(x, y1)
tax2=ax.twinx()
tax2.spines['right'].set_position(('axes',1.09))
make_patch_spines_invisible(tax2)
tax2.spines['right'].set_visible(True)
tax2.plot(x, y2)
'''
ax.set_frame_on(True)
ax.patch.set_visible(False)
for sp in ax.spines.values():
sp.set_visible(False)
def alignYaxes(axes, align_values=None):
'''Align the ticks of multiple y axes
Args:
axes (list): list of axes objects whose yaxis ticks are to be aligned.
Keyword Args:
align_values (None or list/tuple): if not None, should be a list/tuple
of floats with same length as <axes>. Values in <align_values>
define where the corresponding axes should be aligned up. E.g.
[0, 100, -22.5] means the 0 in axes[0], 100 in axes[1] and -22.5
in axes[2] would be aligned up. If None, align (approximately)
the lowest ticks in all axes.
Returns:
new_ticks (list): a list of new ticks for each axis in <axes>.
A new sets of ticks are computed for each axis in <axes> but with equal
length.
'''
from matplotlib.pyplot import MaxNLocator
nax=len(axes)
ticks=[aii.get_yticks() for aii in axes]
if align_values is None:
aligns=[ticks[ii][0] for ii in range(nax)]
else:
if len(align_values) != nax:
raise Exception("Length of <axes> doesn't equal that of <align_values>.")
aligns=align_values
bounds=[aii.get_ylim() for aii in axes]
ticks_align=[ticks[ii]-aligns[ii] for ii in range(nax)]
ranges=[tii[-1]-tii[0] for tii in ticks]
lgs=[-np.log10(rii)+2. for rii in ranges]
igs=[np.floor(ii) for ii in lgs]
log_ticks=[ticks_align[ii]*(10.**igs[ii]) for ii in range(nax)]
comb_ticks=np.concatenate(log_ticks)
comb_ticks.sort()
locator=MaxNLocator(nbins='auto', steps=[1, 2, 2.5, 3, 4, 5, 8, 10])
new_ticks=locator.tick_values(comb_ticks[0], comb_ticks[-1])
new_ticks=[new_ticks/10.**igs[ii] for ii in range(nax)]
new_ticks=[new_ticks[ii]+aligns[ii] for ii in range(nax)]
idx_l=0
for i in range(len(new_ticks[0])):
if any([new_ticks[jj][i] > bounds[jj][0] for jj in range(nax)]):
idx_l=i-1
break
idx_r=0
for i in range(len(new_ticks[0])):
if all([new_ticks[jj][i] > bounds[jj][1] for jj in range(nax)]):
idx_r=i
break
new_ticks=[tii[idx_l:idx_r+1] for tii in new_ticks]
for axii, tii in zip(axes, new_ticks):
axii.set_yticks(tii)
return new_ticks
def plotLines(x, y1, y2, y3, ax):
ax.plot(x, y1, 'b-')
ax.tick_params('y',colors='b')
tax1=ax.twinx()
tax1.plot(x, y2, 'r-')
tax1.tick_params('y',colors='r')
tax2=ax.twinx()
tax2.spines['right'].set_position(('axes',1.2))
make_patch_spines_invisible(tax2)
tax2.spines['right'].set_visible(True)
tax2.plot(x, y3, 'g-')
tax2.tick_params('y',colors='g')
ax.grid(True, axis='both')
return ax, tax1, tax2
if __name__=='__main__':
x=np.arange(20)
y1=np.sin(x)
y2=x/1000+np.exp(x)
y3=x+x**2/3.14
figure=plt.figure(figsize=(12,4),dpi=100)
ax1=figure.add_subplot(1, 3, 1)
axes1=plotLines(x, y1, y2, y3, ax1)
ax1.set_title('No alignment')
ax2=figure.add_subplot(1, 3, 2)
axes2=plotLines(x, y1, y2, y3, ax2)
alignYaxes(axes2)
ax2.set_title('Default alignment')
ax3=figure.add_subplot(1, 3, 3)
axes3=plotLines(x, y1, y2, y3, ax3)
alignYaxes(axes3, [0, 2.2*1e8, 44])
ax3.set_title('Specified alignment')
figure.tight_layout()
figure.show()
ax2.set_ylim((10, 20))
吗? - farenorth