# How to add extra space between the left-side legend and the left parenthesis of a matrix in the presence of a vertical line?

I have the following example:

\documentclass{article}

\usepackage[english]{babel}
\usepackage{booktabs}
\usepackage{array}
\usepackage{blkarray}

\begin{document}

\begin{equation}\label{cexA_Rmat}
\mathbf{R}=
\begin{blockarray}{cccccc}
& \lambda_1 & \lambda_2 & \lambda_3 & \lambda_4 \\
\cmidrule{2-6}
\begin{block}{c|(ccccc)}
\tau_1 &           -1 & \phantom{-}1 & \phantom{-}0 & \phantom{-}0 \\
\tau_2 & \phantom{-}0 &           -1 & \phantom{-}1 & \phantom{-}0 \\
\tau_3 & \phantom{-}0 & \phantom{-}0 & \phantom{-}1 &           -1 \\
\tau_4 &           -1 & \phantom{-}0 & \phantom{-}0 & \phantom{-}1 \\
\end{block}
\end{blockarray}
\end{equation}

\end{document}


where I would like to add extra space between column $\tau_i$ (i=1,2,3,4) and the left-side matrix parenthesis. As you can see in the enclosed image, there the left parenthesis and the vertical line are totally overlapped. How can I increase their distance (as well as the distance between the $\tau_i$s and the vertical line)? ## 2 Answers

Insert a space within the column specification of your blockarray: \documentclass{article}

\usepackage{booktabs}
\usepackage{blkarray}

\begin{document}

$\mathbf{R} = \begin{blockarray}{ cccccc } & \lambda_1 & \lambda_2 & \lambda_3 & \lambda_4 \\ \cmidrule{2-6} \begin{block}{@{} c @{\hspace{1ex}} | @{\quad} (ccccc) } \tau_1 & -1 & \phantom{-}1 & \phantom{-}0 & \phantom{-}0 \\ \tau_2 & \phantom{-}0 & -1 & \phantom{-}1 & \phantom{-}0 \\ \tau_3 & \phantom{-}0 & \phantom{-}0 & \phantom{-}1 & -1 \\ \tau_4 & -1 & \phantom{-}0 & \phantom{-}0 & \phantom{-}1 \\ \end{block} \end{blockarray}$

\end{document}


Also note the removal of the inter-column space (using @{}) at the beginning of the nested block.

• Thanks, you helped a lot! – TobiR Feb 8 at 18:24

With {pNiceArray} of nicematrix.

\documentclass{article}
\usepackage{nicematrix,tikz}

\begin{document}

\mathbf{R}= \begin{pNiceArray}{cccc}[first-col,first-row] & \lambda_1 & \lambda_2 & \lambda_3 & \lambda_4 \\ \hline \noalign{\vskip2pt} \tau_1 & -1 & \phantom{-}1 & \phantom{-}0 & \phantom{-}0 \\ \tau_2 & \phantom{-}0 & -1 & \phantom{-}1 & \phantom{-}0 \\ \tau_3 & \phantom{-}0 & \phantom{-}0 & \phantom{-}1 & -1 \\ \tau_4 & -1 & \phantom{-}0 & \phantom{-}0 & \phantom{-}1 \\ \CodeAfter \tikz \draw ([xshift=-2pt]1-|1) -- ([xshift=-2pt]5-|1) ; \end{pNiceArray}

\end{document} 