For matplotlib, you can label legends and axis labels using tex command syntax. You're supposed to prepend r to the string: r"my tex label". But what I don't understand is why the legend label doesn't care and yet the axis label does care.
Why do the axis labels behave differently than the legend label (or vice versa)?
MWE1 - Crashes
## Hello World! I crash!import numpy as npimport matplotlib.pyplot as pltx = np.ones(5)plt.plot(x, x, label="$\bar{x}$ (but not really)")plt.xlabel("$\bar{y}$ (but not really)") # I cause the crashplt.show()MWE2 - Doesn't Crash
import numpy as npimport matplotlib.pyplot as pltx = np.ones(5)plt.plot(x, x, label="$\bar{x}$ (but not really)") # I still don't need prepended rplt.xlabel(r"$\bar{y}$ (but not really)")plt.show()Best Answer
That's no fair comparison. The plot label from MWE2 get's never used, because there is no legend; therefore it will not raise any error.Once you produce this legend using plt.legend() it will of course cause the same kind of error that you'd expect from all other strings that contain MathText commands and are no raw strings.
This crashes:
import numpy as npimport matplotlib.pyplot as pltx = np.ones(5)plt.plot(x, x, label="$\bar{x}$ (but not really)") plt.xlabel(r"$\bar{y}$ (but not really)")plt.legend()plt.show()Result:
ValueError: $ar{x}$ (but not really)^Expected end of text, found '$' (at char 0), (line:1, col:1)This does not crash, as all strings are raw strings
import numpy as npimport matplotlib.pyplot as pltx = np.ones(5)plt.plot(x, x, label=r"$\bar{x}$ (but not really)") plt.xlabel(r"$\bar{y}$ (but not really)")plt.legend()plt.show()