Question :
In matplotlib you can make the text of an axis label bold by
plt.xlabel('foo',fontweight='bold')
You can also use LaTeX with the right backend
plt.xlabel(r'$phi$')
When you combine them however, the math text is not bold anymore
plt.xlabel(r'$phi$',fontweight='bold')
Nor do the following LaTeX commands seem to have any effect
plt.xlabel(r'$bf phi$')
plt.xlabel(r'$mathbf{phi}$')
How can I make a bold $phi$ in my axis label?
Answer #1:
Unfortunately you can’t bold symbols using the bold font, see this question on tex.stackexchange.
As the answer suggests, you could use boldsymbol to bold phi:
r'$boldsymbol{phi}$'
You’ll need to load amsmath into the TeX preamble:
matplotlib.rc('text', usetex=True)
matplotlib.rcParams['text.latex.preamble']=[r"usepackage{amsmath}"]
Answer #2:
If you intend to have consistently bolded fonts throughout the plot, the best way may be to enable latex and add boldmath to your preamble:
# Optionally set font to Computer Modern to avoid common missing font errors
matplotlib.rc('font', family='serif', serif='cm10')
matplotlib.rc('text', usetex=True)
matplotlib.rcParams['text.latex.preamble'] = [r'boldmath']
Then your axis or figure labels can have any mathematical latex expression and still be bold:
plt.xlabel(r'$frac{phi + x}{2}$')
However, for portions of labels that are not mathematical, you’ll need to explicitly set them as bold:
plt.ylabel(r'textbf{Counts of} $lambda$'}
Answer #3:
In case anyone stumbles across this from Google like I did, another way that doesn’t require adjusting the rc preamble (and conflicting with non-latex text) is:
ax.set_ylabel(r"$mathbf{partial y / partial x}$")
Answer #4:
As this answer Latex on python: alpha and beta don’t work? points out. You may have a problem with b so boldsymbol may not work as anticipated. In that case you may use something like: '$ \boldsymbol{\beta} $' in your python code. Provided you use the preamble plt.rcParams['text.latex.preamble']=[r"usepackage{amsmath}"]
