Center Aligned in A Cell of Table

Question

I would like to have the content in the first and second columns are centered aligned within its respected cells in a table with two column paper template as follows.

The current table is as follows.

Here is the code:

\documentclass[journal]{IEEEtran}
\usepackage{caption}
\usepackage{tabularx}
\begin{document}
\begin{table}[h]
\captionof{table}{Table of $q$ and $z$}
\label{tab:table_q_and_z}
\noindent
\begin{tabularx}{\columnwidth} { | c | c | >{\raggedright\arraybackslash}X |}
  \hline
  \textbf{Steps} & \textbf{$q_i$} & \textbf{Definition of $z_i$}  \
  \hline
  \multirow{$i \leq (n-1)$}  & $q_i$ = 0 & $z_i$ = number of \emph{emptied} chambers at the \emph{cleaning} place $i \leq (n-1)$ \
  \cline{2-3}
                  & \centering $q_i$ = 1 & $z_i$ = number of \emph{loaded} chambers at the \emph{processing} place $i \leq (n-1)$ \
  \hline
   $i=n$  & $q_{n}$ = 0 & $z_n$ = number of \emph{loaded} chambers at the \emph{processing} place $n$ \
   \cline{2-3}
     & $q_{n}$ = 1 & $z_{n}$ = number of \emph{emptied} chambers at the \emph{cleaning} place $n$ \
  \hline
\end{tabularx}
\end{table}
\end{document}

What should be added to the current code?

Answer 1

To achieve vertical centering of the material in the c-type columns, I suggest you execute

\renewcommand\tabularxcolumn[1]{m{#1}}

This is explained in more detail in the user guide of the tabularx package.

I'd also suggest you complete the \multirow commands and -- in the header row -- change \textbf{$q_i$} to \boldmath$q_i$ and change \textbf{Definition of $z_i$} to \boldmath\bfseries Definition of $z_i$, respectively. And, please change $q_i$ = 1 to $q_i = 1$, etc in column 2. I'd further suggest to get rid of the specious \centering instruction and change \captionof{table}{...} to just \caption{...}. (There's no need for \captionof since you're using a table environment.) And, last but not least, consider adding the instruction \setlength\extrarowheight{2pt} to that the table gets a bit less of a compressed "look".

\documentclass[journal]{IEEEtran}
\usepackage{caption}
\usepackage{tabularx}
\renewcommand\tabularxcolumn[1]{m{#1}} % <-- new
\usepackage{multirow}
\begin{document}
\begin{table}[h]
\setlength\extrarowheight{2pt}
\caption{Table of $q$ and $z$}
\label{tab:table_q_and_z}
\noindent
\begin{tabularx}{\columnwidth} { | c | c | >{\raggedright\arraybackslash}X |}
  \hline
  \textbf{Steps} & \boldmath$q_i$ & \boldmath\bfseries Definition of $z_i$  \
  \hline
  \multirow{3}{}{$i \leq (n-1)$}

    & $q_i=0$ 
    & $z_i$ = number of \emph{emptied} chambers at the \emph{cleaning} place $i \leq (n-1)$ \
  \cline{2-3}
    & $q_i=1$ 
    & $z_i$ = number of \emph{loaded} chambers at the \emph{processing} place $i \leq (n-1)$ \
  \hline
  \multirow{3}{}{$i=n$}

    & $q_n=0$ 
    & $z_n$ = number of \emph{loaded} chambers at the \emph{processing} place $n$ \
 \cline{2-3}
    & $q_n=1$ 
    & $z_{n}$ = number of \emph{emptied} chambers at the \emph{cleaning} place $n$ \
  \hline
\end{tabularx}
\end{table}
\end{document}

---

Addendum to address some additional issues with the table:

• The IEEEtran document class is only barely compatible with the caption package. Don't use this package unless the journal you are planning to submit a paper to expressly allows you to use this package.

• The IEEEtran class uses Times Roman as the default text font, but Computer Modern as the default math font. These two fonts are not all that well matched, visually/aesthetically speaking. I'd recommend executing \usepackage{newtxtext,newtxmath} in the preamble to use Times Roman for both text and math.

• Consider getting rid of the all verical lines and most horizontal lines in the table, in order to give the table a much more open and inviting "look". I suggest you use the line-drawing macros of the booktabs package instead of \hline and \cline.

• Using bold-facing in the header row doesn't achieve much, except run the risk of giving the entire table a heavy-handed and potentially vulgar look. Don't over-use bold-facing; for the table at hand, I don't think any bold-facing is needed.

Implementing these ideas, dropping vertical centering in columns 1 and 2, and left-aligning the material in columns 1 and 2, would create the following look. I hope you will agree with me that the table looks a whole lot more inviting and appealing than the one posted above.

\documentclass[journal]{IEEEtran}
\usepackage{tabularx}
\usepackage{newtxtext,newtxmath}
\usepackage{booktabs} % for well-spaced horizontal rules
\usepackage{lipsum}   % filler text
\begin{document}
\begin{table}[h]
\caption{Table of $q$ and $z$}
\label{tab:table_q_and_z}
\begin{tabularx}{\columnwidth} { @{} 
      lll 
      @{\hspace{\tabcolsep}} 
      >{\raggedright\arraybackslash}X 
      @{}}
\toprule
   Steps & $q_i$ 
   & \multicolumn{2}{l}{Definitions of $z_i$ and $z_n$}\
\midrule
$i\leq n-1$ & $q_i=0$ & $z_i$
   & number of \emph{emptied} chambers at the \emph{cleaning} place $i \leq (n-1)$ \
& $q_i=1$ & $z_i$
   & number of \emph{loaded} chambers at the \emph{processing} place $i \leq (n-1)$ \
\addlinespace
$i=n$ & $q_n=0$ & $z_n$
   & number of \emph{loaded} chambers at the \emph{processing} place $n$ \
& $q_n=1$ & $z_n$
   & number of \emph{emptied} chambers at the \emph{cleaning} place $n$ \
\bottomrule
\end{tabularx}
\end{table}
\lipsum
\end{document}

Answer 2

The package nicematrix provides an environment {NiceTabularX} similar to the environment {tabularx} (of the package tabularx) but with, among other features, the ability to add options to the columns X. With X[l,m], you will have a X column which behaves as a m column with a horizontal alignment on the left.

\documentclass[journal]{IEEEtran}
\usepackage{caption}
\usepackage{nicematrix}
\begin{document}
\begin{table}[h]
\captionof{table}{Table of $q$ and $z$}
\label{tab:table_q_and_z}
\noindent
\begin{NiceTabularX}{\columnwidth} {|c|c|X[m,l]|}
  \hline
  \textbf{Steps} & \textbf{$q_i$} & \textbf{Definition of $z_i$}  \
  \hline
  \Block{2-1}{$i \leq (n-1)$}  & $q_i$ = 0 & $z_i$ = number of \emph{emptied} chambers at the \emph{cleaning} place $i \leq (n-1)$ \
  \cline{2-3}
                  & \centering $q_i$ = 1 & $z_i$ = number of \emph{loaded} chambers at the \emph{processing} place $i \leq (n-1)$ \
  \hline
   \Block{2-1}{$i=n$}  & $q_{n}$ = 0 & $z_n$ = number of \emph{loaded} chambers at the \emph{processing} place $n$ \
   \cline{2-3}
     & $q_{n}$ = 1 & $z_{n}$ = number of \emph{emptied} chambers at the \emph{cleaning} place $n$ \
  \hline
\end{NiceTabularX}
\end{table}
\end{document}

However, I recommend a tabular with booktabs in the spirit of booktabs (cf. Mico's answer).

Answer 3

As complement to nice @Mico answer (+1), but with use of the tabularray and bm packages:

• code is a bit shorter
• tabularray syntax for column specification enabled to define math column and simple vertical centering of cells content (option m)
• table lines are defined in table preamble

\documentclass[journal]{IEEEtran}
\usepackage{tabularray}
\usepackage{bm}
\begin{document}
    \begin{table}[h]
    \caption{Table of $q$ and $z$}
    \label{tab:table_q_and_z}
\begin{tblr}{hlines, vlines,
             colspec = { *{2}{Q[c, mode=math]}  X[l, m]},
             row{1}  = {font=\bfseries, mode=text},
             rowsep  = 3pt,
             }
Steps & $\bm{q_i}$ &   Definition of $\bm{z_i}$       \
\SetCell[r=2]{c}    i \leq (n-1) 
    & q_i=0
        & $z_i$: number of \emph{emptied} chambers at the \emph{cleaning}  place $i \leq (n-1)$ \
    & q_i=1
        & $z_i$: number of \emph{loaded} chambers at the \emph{processing} place $i \leq (n-1)$ \
\SetCell[r=2]{c}    i=n
    & q_n=0
        & $z_n$: number of \emph{loaded} chambers at the \emph{processing} place $n$ \
    & q_n=1
        & $z_{n}$: number of \emph{emptied} chambers at the \emph{cleaning} place $n$ \
\end{tblr}
    \end{table}
\end{document}