dot on a subscript mathmode

Question

I am suppressing some of my subindexes in some equations, and I am using a dot in order to signal which dimension is gone. Up to now, I have been using a \bullet symbol as a dot. Is this the "correct" what of doing it, or is there another symbol I am unaware of?

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{align*}
\beta_{kn} &\sim \left(1\times 1\right) \\
\boldsymbol{\beta}_{k\bullet} &= \left(\beta_{k1},\dots,\beta_{kN}\right) \sim \left(N\times 1\right) \\
\boldsymbol{\beta}_{\bullet n} &= \left(\beta_{1n},\dots,\beta_{Kn}\right) \sim \left(1\times K\right)
\end{align*}
\end{document}

Answer 1

I like use _ instead of dot.

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{align*}
\beta_{kn}                & \sim \left(1\times 1\right)                                            \\
\boldsymbol{\beta}_{k\_}  & = \left(\beta_{k1},\dots,\beta_{kN}\right) \sim \left(N\times 1\right) \\
\boldsymbol{\beta}_{\_ n} & = \left(\beta_{1n},\dots,\beta_{Kn}\right) \sim \left(1\times K\right)
\end{align*}
\end{document}