How to do left and top descriptions of a cross table?

Question

Is it possible to make a table as this in a \begin{tabular}...\end{tabular} kind of thing? I didn't even really know what to search for, so I didn't find anything on the internet. And a solution without using tikz would be greatly appreciated as I struggle to understand what's going on in tikz.

Thanks for any help!

Answer 1

Just use multirow.

\documentclass[12pt,a4paper]{article}
  \usepackage{multirow}
\begin{document}
 
    \begin{table}[ht]
    \caption{Multi-row table}
    \begin{center}
    \begin{tabular}{c|c|c|c|c}
    \multicolumn{2}{c}{}&\multicolumn{2}{c}{\textbf{Y}}&\\\cline{3-4}
    \multicolumn{2}{c|}{}&$b_{1}$&$b_{2}$&$\sum$\\\cline{2-4}
    \multirow{2}{*}{\textbf{X}} & $a_1$ & & 12 & 34\\\cline{2-4}
    & $a_2$ & & & 63\\\cline{2-4}     
    \multicolumn{1}{c}{}& \multicolumn{1}{c}{$\sum$} & \multicolumn{1}{c}{55} & \multicolumn{1}{c}{42} & \multicolumn{1}{c}{97}\\     
    \end{tabular}
    \end{center}
    \label{tab:XY}
    \end{table}


\end{document}

Answer 2

With {NiceMatrix} of the package nicematrix.

\documentclass{article}
\usepackage{nicematrix}

\begin{document}

$\begin{NiceMatrix}[first-row,last-row=4,first-col,last-col=4,hvlines,corners=NW]
               &      & \Block{1-2}{Y} \\
               &      & b_1 & b_2 & \sum \\
\Block{2-1}{X} & a_1  &     & 12  & 34 \\
               & a_2  &     &     & 63 \\
               & \sum & 55  & 42  & 97 \\
\end{NiceMatrix}$

\end{document}

You need several compilations (because nicematrix uses PGF/Tikz nodes under the hood).