I'm not sure how to do this and have spent a long time trying.
I looked at a previous post on this: Bold subscripts
It is slightly different but, I still can't get it to work.
My code:
\begin{equation}
p(\textbf{x}) = \sum_{n=1}^{K} \pi_k \mathcal{N}
(\textbf{x}|\mathbf{\mu}_{k},\mathbf{\Sigma}_{k})
\end{equation}
As you can see, I can get the sigma in bold, but not the mu?
Thanks in advance
Best Answer
I am adding an answer for a remark (the OP got the answer from @Manuel's comment to use
\bm
frombm
package; one can also use\boldsymbol
fromamsmath
package).The remark here is that there was a problem with
\mu
but not with\Sigma
. Why?The point is that the cmr font contains 11 uppercase greek letters in slots 0 to 10, in the OT1 encoding. This is a bizarre legacy, but it does make
\mathbf{\Sigma}
work. I.e. the font used for operator names (log
,sin
,cos
,...) also contains the uppercase (non-Latin) Greek letters. The idea of the\math..
alphabet commands is to use the text font in math mode. That it works for those 11 Greek letters is counter-intuitive and bound to the OT1 encoding used by the "operator" font. It is not robust against changes of the "operator" font.Hence I would not recommend using
\mathbf{\Sigma}
, because it twists too much the idea of the LaTeX NFSS math alphabet commands. It ties it to peculiarity of Knuth's OT1 encoding.