科学记数法 pyplot 子图中的小数位数

Question

我正在用不同 y 轴的子图制作图形。最后一个图的 y 轴需要用科学计数法表示，我希望轴上的数字只显示 2 位小数，即 2.15 而不是 2.1565。我一直在尝试格式化数字数小时但没有成功。关于如何操作有什么建议吗？

import matplotlib.pyplot as plt
import numpy as np
import matplotlib.ticker as mtick
from matplotlib.ticker import FormatStrFormatter


fig, axs = plt.subplots(2, 3)
y_pos = [0.2,0.4,0.6,0.8]


plt.setp(axs, xticks=[0.2,0.4,0.6,0.8], xticklabels=['A','B','C','D'],xlim=[0.1,0.9],facecolor='#F4F4F4')


#P-2

Pval = [3.3705E+00,3.4262E+00,3.5093E+00,3.4882E+00]

axs[0,0].set_ylim(3.3,3.55)
axs[0,0].set_yticks(np.arange(3.3,3.56, 0.05))
axs[0,0].grid(zorder=0)
axs[0,0].bar(y_pos,Pval,width=0.1,color='#ADDDCE')
axs[0,0].set_title(r'$Initial$') 
axs[0,0].grid(True,linestyle='--',color='#D6D8CD')





#P-1


Pval = [1.6667E+00,1.6079E+00,1.6087E+00,1.6132E+00]

axs[0,1].set_ylim(1.5,1.7)
axs[0,1].set_yticks(np.arange(1.5,1.71, 0.05))
axs[0,1].grid(zorder=0)
axs[0,1].bar(y_pos,Pval,width=0.1,color='#FFC347')

axs[0,1].set_title(r'$Test 1$') 
axs[0,1].grid(True,linestyle='--',color='#D6D8CD')







#P1

Pval = [9.9458E-01,9.4241E-01,9.4569E-01,9.4014E-01]
axs[0,2].set_ylim(0.8,1)
axs[0,2].set_yticks(np.arange(0.8,1.01, 0.05))

#
axs[0,2].grid(zorder=0)
axs[0,2].bar(y_pos,Pval,width=0.1,color='#FC746C')
# 
axs[0,2].set_title(r'$Test 2$') 
axs[0,2].grid(True,linestyle='--',color='#D6D8CD')





#P2


Pval = [2.4196E+00,2.3292E+00,2.3499E+00,2.3213E+00]
axs[1,0].set_ylim(1.8,2.5)
axs[1,0].set_yticks(np.arange(1.8,2.7, 0.2))
#
axs[1,0].grid(zorder=0)
axs[1,0].bar(y_pos,Pval,width=0.1,color='#70AE98')
# 
axs[1,0].set_title(r'$  \omega  $') 
axs[1,0].grid(True,linestyle='--',color='#D6D8CD')



#P3



Pval = [1.5646E+01,1.5346E+01,1.5538E+01,1.5298E+01]
axs[1,1].set_ylim(15,15.7)
axs[1,1].set_yticks(np.arange(15.,15.9, 0.2))

#X
axs[1,1].grid(zorder=0)
axs[1,1].bar(y_pos,Pval,width=0.1,color='#F0A35E')
#
axs[1,1].set_title(r'$  \Pi  $') 
axs[1,1].grid(True,linestyle='--',color='#D6D8CD')


#P4

Pval = [2.1391E+02,2.1148E+02,2.1434E+02,2.1085E+02]
axs[1,2].set_ylim(2.09E+02,2.15E+02)
axs[1,2].set_yticks(np.arange(2.09E+02,2.16E+02,0.95))
#axs[1,2].ticklabel_format(style='sci',scilimits=(200,300),axis='y')
#
#axs[1,2].yaxis.set_major_formatter(MathTextSciFormatter('%.2e'))

#m = grabMaxExponent(2)
#axs[1,2].yaxis.set_major_formatter(OOMFormatter(2, "%1.1f"))
#axs[1,2].yaxis.set_major_formatter(mtick.FormatStrFormatter('%.2f'))


axs[1,2].ticklabel_format(axis='y', style='sci', scilimits=(2,2))
axs[1,2].yaxis.major.formatter._useMathText = True
#axs[1,2].yaxis.set_major_formatter(FormatStrFormatter('%.2f'))
#axs[1,2].yaxis.set_major_formatter(MathTextSciFormatter('%.2e'))
#axs[1,2].ticklabel_format(useOffset=False)
#X
axs[1,2].grid(zorder=0)
axs[1,2].bar(y_pos,Pval,width=0.1,color='#CA7E8D')
# 
axs[1,2].set_title(r'$\gamma$') 
axs[1,2].grid(True,linestyle='--',color='#D6D8CD')


fig.tight_layout()
plt.show()

Answer 1

ScalarFormatter 不支持自定义格式。您可以尝试的是覆盖负责格式化的方法：

（注意：这适用于 Matplotlib 3.0.x - Python 3.x，不适用于 Matplotlib 2.0.x .)

from matplotlib.ticker import ScalarFormatter
...
# P4

# Extend ScalarFormatter
class MyScalarFormatter(ScalarFormatter):
    # Override '_set_format' with your own
    def _set_format(self):
        self.format = '%.2f'  # Show 2 decimals

# Your data as before
Pval = [2.1391E+02,2.1148E+02,2.1434E+02,2.1085E+02]
axs[1,2].set_ylim(2.09E+02,2.15E+02)
axs[1,2].set_yticks(np.arange(2.09E+02,2.16E+02,0.95))

# New code
custom_formatter = MyScalarFormatter(useMathText=True)
axs[1,2].yaxis.set_major_formatter(custom_formatter)
axs[1,2].yaxis.major.formatter.set_powerlimits((2,2))
#axs[1,2].yaxis.major.formatter.set_scientific(True)  # Redundant: True is default

# Rest code as before
axs[1,2].grid(zorder=0)
axs[1,2].bar(y_pos,Pval,width=0.1,color='#CA7E8D')
axs[1,2].set_title(r'$\gamma$') 
axs[1,2].grid(True,linestyle='--',color='#D6D8CD')

fig.tight_layout()
plt.show()

输出

不过，它四舍五入 你的 y 轴值。但是你可以通过这种方式稍微解决一下以获得你想要的结果。看看 ScalarFormatter source.

科学记数法 pyplot 子图中的小数位数

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输出