I'm trying to set-up the column width of a bordermatrix with the usual \setlength{\arraycolsep}{0pt} command (usual in the sense that it works for usual matrices) without success: what should I use instead?
[Tex/LaTex] bordermatrix with thinner columns
bordermatrix
Related Solutions
The blkarray package allows to do complex border matrix with relatively simple code:
\documentclass{article}
\usepackage{blkarray}
\usepackage{multirow}
\begin{document}
\[
\begin{blockarray}{cc|cccc|cccc}
& 1\dots 18 & 19 & 20 & 21 & 22 & 23 & 24 & 25 & 26 \\
\begin{block}{c(c|cccc|cccc@{\hspace*{5pt}})}
A'_1 & A_1 & \BAmulticolumn{4}{c|}{\multirow{4}{*}{$I$}}&\BAmulticolumn{4}{c}{\multirow{4}{*}{$I$}}\\
A'_2 & A_2 & &&&&&&&\\
A'_3 & A_3 & &&&&&&&\\
A'_4 & A_4 & &&&&&&&\\
\cline{1-10}% don't use \hline
B'_1 & B_1 & \BAmulticolumn{4}{c|}{\multirow{4}{*}{$J$}}&\BAmulticolumn{4}{c}{\multirow{4}{*}{$I$}}\\
B'_2 & B_2 & &&&&&&&\\
B'_3 & B_3 & &&&&&&&\\
B'_4 & B_4 & &&&&&&&\\
\end{block}
\end{blockarray}
\]
\end{document}
You can add a couple of patches:
\documentclass{article}
\usepackage{etoolbox}
\let\bbordermatrix\bordermatrix
\patchcmd{\bbordermatrix}{8.75}{4.75}{}{}
\patchcmd{\bbordermatrix}{\left(}{\left[}{}{}
\patchcmd{\bbordermatrix}{\right)}{\right]}{}{}
% Add some space between rows
\patchcmd{\bbordermatrix}{\begingroup}{\begingroup\openup1\jot}{}{}
% Add the same amount at the end
\makeatletter
\patchcmd{\bbordermatrix}
{\vcenter{\kern-\ht\@ne\unvbox\z@\kern-\baselineskip}}
{\vcenter{\kern-\ht\@ne\unvbox\z@\kern-\baselineskip\kern2pt}}
{}{}
\makeatother
\begin{document}
\[
\mathbf{P}=\bbordermatrix{& 0 & 1 & 2\cr
0 & 0 & \frac{1}{2} & \frac{1}{2}\cr
1 & \frac{1}{2} & 0 & \frac{1}{2}\cr
2 & \frac{1}{2} & \frac{1}{2} & 0}
\]
\end{document}
Best Answer
\quadis used as seperator.