inner-column labeled matrix

Question

I am slowly becoming more efficient with math environments and macros in TeX, but occasionally come across something where I'm not really sure what the best solution would be.

I wanted to hear from some experts what you think would be the most sensible approach (looks good and efficient to code) to making the above figure in LaTeX. I was initially thinking

1. tabular using \multicolumn,
2. TikZ; then
3. array.

Not necessarily looking for someone to just write me a solution, but more of insight into your macro/environment approach and why.

Answer 1

I tend to favour the ordinary use of environments like tabular or array, since it makes the solution easily portable without any bells or whistles. Simplicity perhaps.

Based on the display, I'm going for an array with one column for the left hand descriptors, and 12 columns for the arrangement on the right:

\documentclass{article}
\begin{document}
\[
  \begin{array}{r@{\quad}*{12}{c@{\mskip10mu}}}
    & n-2 & & n-1 & & & n & & & n+1 & & & n+2 \\
    \mbox{Equilibrium:} & \bullet & & \bullet & & & \bullet & & & \bullet & & & \bullet \\
    & \phantom{{\leftarrow}}{\!|\!}{\leftarrow} & a & {\rightarrow}{\!|\!}\phantom{{\rightarrow}} & \\
    \mbox{Displaced:} & \ooalign{$\bullet$\cr\hidewidth${|}$\hidewidth} & & {|} & & \bullet & {|} & & \bullet & {|} & & \bullet & \ooalign{$\bullet$\cr\hidewidth${|}$\hidewidth} \\
    & & & {\rightarrow}{\!|\!}\phantom{{\rightarrow}} & \makebox[0pt]{$u_{n-1}$} & \phantom{{\leftarrow}}{\!|\!}{\leftarrow} &
      {\rightarrow}{\!|\!}\phantom{{\rightarrow}} & \makebox[0pt]{$u_n$} & \phantom{{\leftarrow}}{\!|\!}{\leftarrow} &
      {\rightarrow}{\!|\!}\phantom{{\rightarrow}} & \makebox[0pt]{$u_{n+1}$} & \phantom{{\leftarrow}}{\!|\!}{\leftarrow}
  \end{array}
\]
\end{document}