[Tex/LaTex] Multicolumn in table not centered

horizontal alignmenttables

I have some issues with the usage of \multicolumn. As can be seen on the screenshot below, the words 'Classical' and 'Squared' are correctly aligned in the centre of the column. The word 'Exponential' however is not centered properly.

The code is:

\begin{table}[]
\setlength{\tabcolsep}{12pt}
\centering
\begin{tabular}{l c c c c c c}
\hline\hline
\\\\[-4.3\medskipamount]
 & \multicolumn{2}{c}{Classic} & \multicolumn{2}{c}{Squared} & \multicolumn{2}{c}{Exponential} \\
\textit{a} & 70 & 30 & 70 & 30 & 70 & 30 \\ [0.5ex]
\hline
\\\\[-3.9\medskipamount]
S100 & 91 & 31 & 71 & 01 & 21 & 41 \\
S100 & 91 & 31 & 71 & 01 & 21 & 41 \\
S100 & 91 & 31 & 71 & 01 & 21 & 41 \\
[1ex] \hline
\end{tabular}
\end{table}

I would prefer to keep using the tabular package in the solution. Thank you in advance!

Best Answer

The reason is that this word is a bit too long. Of course, you can increase the value of \tabcolsep. Another solution uses a \makebox[0pt], which allows the word to overlap slightly into the inter-column space, symmetrically.

Other than that,I recommend using the rules from booktabs, which have a variable thickness, and add some vertical padding around the rules. This will save you from adjusting by hand through spacing:

\documentclass{article}
\usepackage{booktabs} 

\begin{document}

\begin{table}[]
\setlength{\tabcolsep}{12pt}
\centering
\begin{tabular}{l c c c c c c}
\toprule\midrule
 & \multicolumn{2}{c}{Classic} & \multicolumn{2}{c}{Squared} & \multicolumn{2}{c}{\makebox[0pt]{Exponential}} \\
\textit{a} & 70 & 30 & 70 & 30 & 70 & 30 \\ [0.5ex]
\midrule
\\\\[-3.9\medskipamount]
S100 & 91 & 31 & 71 & 01 & 21 & 41 \\
S100 & 91 & 31 & 71 & 01 & 21 & 41 \\
S100 & 91 & 31 & 71 & 01 & 21 & 41 \\
\bottomrule
\end{tabular}
\end{table}

\end{document}

Related Solutions

[Tex/LaTex] tabu package – gaps in vertical lines

One way is to shift up the skip prior to the mid-height \tabucline with a \\[-1pt]. See below for 2nd approach.

%Dokumentclass
\documentclass[landscape]{letter}

%Packages
\usepackage[landscape]{geometry}
\usepackage[utf8]     {inputenc}
\usepackage           {multirow}
\usepackage           {tabu}

%Formatting
\pagestyle{empty} %Remove numbering

\begin{document}
  \begin{tabu}{ |[1pt] l | l l | l | l |[1pt] }
                                                                                                                 \tabucline[1 pt]{1-5}
    \multicolumn{2}{ |[1pt] l }{ } & \multicolumn{3}{ |[1pt] l |[1pt]}{ }                                     \\                       \hline
    &                              & \multicolumn{1}{ |[1pt] l |     }{ } & \multicolumn{2}{  l |[1pt] }{ }   \\                       \hline
 y   &                              & \multicolumn{1}{ |[1pt] l |     }{ } & \multicolumn{2}{  l |[1pt] }{ }   \\[-1pt]   \tabucline[1 pt]{3-5} 
\hline
 x   &                              & \multicolumn{1}{ |[1pt] l |     }{ } &                                 & \\                       \hline
    &                              & \multicolumn{1}{ |[1pt] l |     }{ } &                                 & \\                       \hline
    &                              & \multicolumn{1}{ |[1pt] l |     }{ } &                                 & \\                       \hline
    &                              & \multicolumn{1}{ |[1pt] l |     }{ } &                                 & \\ \tabucline[1 pt]{1-5}
  \end{tabu}
\end{document}

enter image description here

Alternately, if you want the thin line to bisect the thick line, then the approach: \\[-1pt] \tabucline[1 pt]{3-5}\\[-12.5pt]\hline works.

%Dokumentclass
\documentclass[landscape]{letter}

%Packages
\usepackage[landscape]{geometry}
\usepackage[utf8]     {inputenc}
\usepackage           {multirow}
\usepackage           {tabu}

%Formatting
\pagestyle{empty} %Remove numbering

\begin{document}
  \begin{tabu}{ |[1pt] l | l l | l | l |[1pt] }
                                                                                                                 \tabucline[1 pt]{1-5}
    \multicolumn{2}{ |[1pt] l }{ } & \multicolumn{3}{ |[1pt] l |[1pt]}{ }                                     \\                       \hline
    &                              & \multicolumn{1}{ |[1pt] l |     }{ } & \multicolumn{2}{  l |[1pt] }{ }   \\                       \hline
 y   &                              & \multicolumn{1}{ |[1pt] l |     }{ } & \multicolumn{2}{  l |[1pt] }{ }   \\[-1pt]   \tabucline[1 pt]{3-5}\\[-12.5pt]
\hline
 x   &                              & \multicolumn{1}{ |[1pt] l |     }{ } &                                 & \\                       \hline
    &                              & \multicolumn{1}{ |[1pt] l |     }{ } &                                 & \\                       \hline
    &                              & \multicolumn{1}{ |[1pt] l |     }{ } &                                 & \\                       \hline
    &                              & \multicolumn{1}{ |[1pt] l |     }{ } &                                 & \\ \tabucline[1 pt]{1-5}
  \end{tabu}
\end{document}

enter image description here

Table entry not centered

The text "Left" and "Right" are actually centered, it is just that the "Left" and "Right" columns are of different size. We can remedy this with a fixed width centered column type.

\documentclass[twocolumn]{book}
\usepackage   {lipsum}
\usepackage   {subfig}
\usepackage   {tikz}
\usepackage{booktabs, array}%<--
\newcolumntype{x}[1]{>{\centering\arraybackslash\hspace{0pt}}p{#1}}%<--

\begin{document}
\begin{table}
\setlength{\tabcolsep}{3pt}
\scriptsize
\centering
\caption{XXX}

\begin{tabular}{l|x{.5in}x{.5in}|x{.5in}x{.5in}|x{.5in}x{.5in}}%<--
\toprule
& \multicolumn{2}{c|}{AAAAAAAAAAAAAA} & \multicolumn{2}{c|}{AAAAAAAAAAAAAA} & \multicolumn{2}{c}{AAAAAAAAAAAAAA} \\
\textbf{Recognition} & Left & Right & Left & Right & Left & Right \\
\midrule
Without Context & 0.65 & 0.17 & - & 0.87 & 0.82 & 0.50 \\
With Context & 0.60 & 0.58 & - & 0.94 & 0.77 & 0.38 \\
\bottomrule
& & & & & & \\
\toprule
& \multicolumn{2}{c|}{AAAAAAAAAAAAAA} & \multicolumn{2}{c|}{AAAAAAAAAAAAAA} & \multicolumn{2}{c}{AAAAAAAAAAAAAA} \\
\textbf{Anticipation} & Left & Right & Left & Right & Left & Right \\
\midrule
Without Context & 0.25 & - & 0.84 & 0.60 & 0.85 & 0.34 \\
With Context & 0.24 & - & 0.98 & 0.65 & 0.72 & 0.13 \\
\bottomrule
\end{tabular}

\end{table}
\end{document}

EDIT: Note my choice of .5in was arbitrary but fortunately close to @Mico's subsequent actual calculation of ~.53 inches. The difference in output is slight, but noticeable with calipers. Please see @Mico's excellent answer for those computations.

Best Answer

Related Solutions

[Tex/LaTex] tabu package – gaps in vertical lines

Table entry not centered

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