表格左下括号居中

Question

我编写了这个代码是为了获得一个简单的 I x J 矩阵。

\begin{table}[H]
        \caption{Invidual/Attributes Matrix}
\begin{center}
\scalebox{1.2}{
    \begin{tabular}{crc|c|c|c|c|}
        \cline{4-7}
        \multirow{5}{22.5mm}{\texttt{Individuals}}\ldelim\{{5}{.8mm}
       && &$a_{11}$&    $a_{12}$  &\dots  &$a_{1J}$  \\ \cline{4-7}
&&  &$a_{21}$& $a_{22}$ &\dots  &$a_{2J}$  \\ \cline{4-7}
&&  &$a_{31}$&$a_{31}$  &\dots  & $a_{3J}$ \\ \cline{4-7}
&&  &\vdots & \vdots &\ldots &\vdots  \\ \cline{4-7} 
&&  &$a_{I1}$&$a_{I1}$  &\dots  &$a_{IJ}$  \\ \cline{4-7}
    & & \multicolumn{1}{c}{} & \multicolumn{4}{c}{\begin{minipage}[c][20mm][c]{24mm}\begin{center}$\underbrace{\hspace*{27.5mm}}$\\\texttt{Attributes} \\ \texttt{$ J $ Elements} \end{center} \end{minipage}} \\
\end{tabular} 
}
\end{center}
\end{table}

这是输出：

我有两个问题：

1. 我希望矩阵位于标题下方的中心，而不是所有内容，以便个人和左括号位于左侧
2. 我希望左括号和矩阵之间的距离更小

Answer 1

使用简单的array：

\documentclass{article}
\usepackage{caption}% For space under caption
\begin{document}

\begin{table}
\caption{Invidual/Attributes Matrix}
\centering
\makebox[0pt][r]{\texttt{Individuals}}
$\left\{\rule{0pt}{1.4cm}\right.%
  \underbrace{\begin{array}{|c|c|c|c|}\hline
  a_{11} & a_{12}  &\dots  &a_{1J}  \\ \hline
  a_{21} & a_{22} &\dots  &a_{2J}  \\ \hline
  a_{31} & a_{31}  &\dots  & a_{3J} \\ \hline
  \vdots & \vdots &\ldots &\vdots  \\ \hline 
  a_{I1} & a_{I1}  &\dots  &a_{IJ}  \\ \hline 
  \multicolumn{1}{c}{\vspace{-0.6\normalbaselineskip}}
\end{array}}_{\texttt{\normalsize\shortstack{~\\Attributes\\$J$ Elements}}}$ 
\end{table} 

\end{document}

Answer 2

您可以将矩阵存储在一个框中，并在放置标签时使用它来测量高度Individuals。此外，要将矩阵放置在标题的水平中心，请将标签设置Individuals在零宽度框内。

\documentclass{article}

\usepackage{amsmath}

\begin{document}

\begin{table}
  \caption{Invidual/attributes Matrix}
  \[
    \sbox0{% Store the matrix in a box
      $\begin{array}{ | c | c | c | c | }
        \hline
        a_{11} & a_{12} & \dots  & a_{1J} \\
        \hline
        a_{21} & a_{22} & \dots  & a_{2J} \\
        \hline
        a_{31} & a_{32} & \dots  & a_{3J} \\
        \hline
        \vdots & \vdots & \ddots & \vdots \\
        \hline
        a_{I1} & a_{I2} & \dots  & a_{IJ} \\
        \hline
      \end{array}$%
    }
    \underbrace{
      \makebox[0pt][r]{$
        \texttt{Individuals}
        \left\{
          \vphantom{\usebox0}
        \right.
        \kern-\nulldelimiterspace$%
      }
      \usebox0
    }_{
      \begin{tabular}{ c }
        \ttfamily Attributes \\
        \ttfamily $J$ elements
      \end{tabular}
    }
  \]

\end{table}

Answer 3

经过一些测量：

\documentclass{article}
\usepackage{amsmath}
\usepackage{array}

\begin{document}

\begin{table}[htp]

\caption{Invidual/Attributes Matrix}

\[
\sbox0{%
  \texttt{Individuals }%
  $\left\{\begin{array}{@{}c@{}}\\\\\\\\\end{array}\right.$%
}
\underbrace{\kern-\wd0
  \texttt{Individuals }\left\{
  \begin{array}{|c|c|c|c|}
  \hline
  a_{11} & a_{12} & \dots  & a_{1J} \\
  \hline
  a_{21} & a_{22} & \dots  & a_{2J} \\
  \hline
  a_{31} & a_{32} & \dots  & a_{3J} \\
  \hline
  \vdots & \vdots & \ddots & \vdots \\
  \hline
  a_{I1} & a_{I2} & \dots  & a_{IJ} \\
  \hline
  \end{array}\right.
}_{\begin{tabular}{@{}>{\ttfamily}c@{}}Attributes \\ $J$ Elements\end{tabular}}
\kern-\wd0
\]

\end{table}

\end{document}