Put names on top of matrix

Question

I am trying to produce 3 matrices on the same line. And on top of the each matrix, there is a name. I tried using tabular for the names and then I use align for the matrices. However, this creates some kind of space between the names and the matrices, which I do not want. Is there a better way to do this ? I have seen other posts but they do not seem to solve my problem. Please note that I need to use bordermatrix because I need to label the rows and columns as well.

\begin{center}
\begin{tabular}{ccc}
Kay & Brian &  Edwin \\
\end{tabular}
\end{center}
\begin{align*}
\bordermatrix{ & I & A \cr
I &1 & 2 \cr
A & 3 & 4
} 
&
\bordermatrix{ & I & A \cr
I &5 & 6 \cr
A & 7 & 8
} 
&
\bordermatrix{ & I & A \cr
I &9 & 10 \cr
A & 11 & 12
} 
\end{align*}

Answer 1

The optional argument to \stackon which I set to 3pt, is the spacing between the matrix and the name.

\documentclass{article}
\usepackage{amsmath}
\usepackage[usestackEOL]{stackengine}[2013-09-11]

\begin{document}
\(
\stackon[3pt]{%
\bordermatrix{ & I & A \cr
I &1 & 2 \cr
A & 3 & 4
}%
}{Kay}\quad
\stackon[3pt]{%
\bordermatrix{ & I & A \cr
I &5 & 6 \cr
A & 7 & 8
}%
}{Brian}\quad
\stackon[3pt]{%
\bordermatrix{ & I & A \cr
I &9 & 10 \cr
A & 11 & 12
} %
}{Edwin}
\)
\end{document}

Answer 2

The following example converts \bordermatrix to a math operator \mathop that allows putting a "limit" (superscript) on top of it.

Just for fun, two variants follow:

1. Curly brace over the matrix below the label.

2. Matrix label in the top left corner of the matrix.

\documentclass{article}
\usepackage{amsmath}

\newcommand*{\topbordermatrix}[2]{%
  {\mathop{\bordermatrix{#2}}\limits^{\mbox{#1}}}%
}

\begin{document}
  \begin{align*}
    \topbordermatrix{Kay}{ & I & A \cr
    I &1 & 2 \cr
    A & 3 & 4
    }
    &&
    \topbordermatrix{Brian}{ & I & A \cr
    I &5 & 6 \cr
    A & 7 & 8
    }
    &&
    \topbordermatrix{Edwin}{ & I & A \cr
    I &9 & 10 \cr
    A & 11 & 12
    }
  \end{align*}

  \renewcommand*{\topbordermatrix}[2]{%
    {\overbrace{\bordermatrix{#2}}^{\mbox{#1}}}%
  }
  \begin{align*}
    \topbordermatrix{Kay}{ & I & A \cr
    I &1 & 2 \cr
    A & 3 & 4
    }
    &&
    \topbordermatrix{Brian}{ & I & A \cr
    I &5 & 6 \cr
    A & 7 & 8
    }
    &&
    \topbordermatrix{Edwin}{ & I & A \cr
    I &9 & 10 \cr
    A & 11 & 12
    }
  \end{align*}

  \renewcommand*{\topbordermatrix}[2]{%
    {\settowidth{\dimen0}{$\scriptstyle\text{#1}$}\kern\dimen0}%
    {\settowidth{\dimen0}{$A$}\kern-\dimen0}%
    \kern-\tabcolsep
    \bordermatrix{\hfill\llap{$\scriptstyle\text{#1}$}\kern-\tabcolsep #2}%
  }  
  \begin{align*}
    \topbordermatrix{Kay}{ & I & A \cr
    I &1 & 2 \cr
    A & 3 & 4
    } 
    &&
    \topbordermatrix{Brian}{ & I & A \cr
    I &5 & 6 \cr
    A & 7 & 8
    } 
    &&
    \topbordermatrix{Edwin}{ & I & A \cr
    I &9 & 10 \cr
    A & 11 & 12
    }
  \end{align*} 
\end{document}

Answer 3

With {pNiceMatrix} of nicematrix.

\documentclass{article}
\usepackage{nicematrix}

\begin{document}

\begin{center}
\NiceMatrixOptions{first-row,first-col}
\setlength{\tabcolsep}{10pt}
\begin{tabular}{ccc}
Kay & Brian & Edwin \\
$\begin{pNiceMatrix}
  & I & A \\
I & 1 & 2 \\
A & 3 & 4
\end{pNiceMatrix}$
&
$\begin{pNiceMatrix}
  & I & A \\
I & 5 & 6 \\
A & 7 & 8
\end{pNiceMatrix}$
&
$\begin{pNiceMatrix}
  & I  & A \\
I & 9  & 10 \\
A & 11 & 12
\end{pNiceMatrix}$
\end{tabular}
\end{center}

\end{document}