LaTeX导入matplotlib生成的PGF文件失败：坐标轴字体相关问题

此前一直正常绘图，将某张图保存为PGF格式后，未对相关配置做任何改动，但LaTeX编译突然失效。

绘图代码 #

import matplotlib.pyplot as plt
import numpy as np
from pathlib import Path
import matplotlib.cm as cm
import tikzplotlib
import matplotlib as mpl

mpl.rcParams['mathtext.fontset'] = 'cm' # Latex font
mpl.rcParams['font.family'] = 'serif'
mpl.rcParams['font.serif'] = ['cmr10']
mpl.rcParams['axes.formatter.use_mathtext'] = True

# Erzeuge eine Liste von x-Werten
x = np.linspace(-5, 10, 100)
a= [2,8,8,2]
b=[2,2,8,2]

U_1=2
U_2=8
I_1=2
I_2=8

# Berechne die entsprechenden y-Werte für die Funktion y = x
y = x

# Plotte die Funktion
plt.plot(x, y)
plt.plot(a,b, color = 'crimson', marker='', linestyle='dashed')
plt.plot(U_1,I_1, color = 'green', marker='x', linestyle='',label='$(U_{1}, I_{1})$', markersize=14)
plt.plot(U_2,I_2, color = 'orange', marker='x', linestyle='',label='$(U_{1}, I_{2})$', markersize=14)
plt.plot(U_2,I_1, color = 'purple', marker='x', linestyle='',label='$(U_{2}, I_{2})$', markersize=14)

# Beschriftungen für die Achsen hinzufügen
plt.xlabel('$I$ / arbitrary units')
plt.ylabel('$U$ / arbitrary units')

# Titel für den Plot hinzufügen
plt.title('Beispiel Fit')
plt.legend(loc='upper left')

# Grid hinzufügen
plt.grid(True)

# Den Plot anzeigen
plt.savefig('example.pgf', format='pgf', bbox_inches='tight', pad_inches = 0)
plt.show()

问题定位 #

经排查，问题出在以下两行Matplotlib配置：

mpl.rcParams['font.serif'] = ['cmr10']
mpl.rcParams['axes.formatter.use_mathtext'] = True

注释配置后的现象 #

若注释掉这两行，LaTeX编译可正常进行，但会出现两个问题：

• 坐标轴字体显示异常
• 对数刻度无法呈现LaTeX风格的10^{-21}格式

LaTeX编译错误信息 #

! Undefined control sequence.
<recently read> \mathdefault
l.109 ...\catcode`\%=\active\def%{\%}$\mathdefault
{\ensuremath{-}4}$}}%
The control sequence at the end of the top line
of your error message was never \def'ed. If you have
misspelled it (e.g., `\hobx'), type `I' and the correct
spelling (e.g., `I\hbox'). Otherwise just continue,
and I'll forget about whatever was undefined.
! Undefined control sequence.
<recently read> \mathdefault
l.147 ...\catcode`\%=\active\def%{\%}$\mathdefault
{\ensuremath{-}2}$}}%
The control sequence at the end of the top line
of your error message was never \def'ed. If you have
misspelled it (e.g., `\hobx'), type `I' and the correct
spelling (e.g., `I\hbox'). Otherwise just continue,
and I'll forget about whatever was undefined.
! Undefined control sequence.
<recently read> \mathdefault
l.185 ...\catcode`\%=\active\def%{\%}$\mathdefault
{0}$}}%
The control sequence at the end of the top line
of your error message was never \def'ed. If you have
misspelled it (e.g., `\hobx'), type `I' and the correct
spelling (e.g., `I\hbox'). Otherwise just continue,
and I'll forget about whatever was undefined.
! Undefined control sequence.
<recently read> \mathdefault
l.223 ...\catcode`\%=\active\def%{\%}$\mathdefault
{2}$}}%
The control sequence at the end of the top line
of your error message was never \def'ed. If you have
misspelled it (e.g., `\hobx'), type `I' and the correct
spelling (e.g., `I\hbox'). Otherwise just continue,
and I'll forget about whatever was undefined.
...

内容的提问来源于stack exchange，提问作者L_physics