Coloring columns in blockarray

Question

I'd like to color individual columns in a 3x3 matrix created using \blockarray. I wish to give one color to the first column, and a second color to the 2nd and 3rd column. I found the answers two this question helpful, however, they do not seem to solve my problem.

However, I somehow cannot get the first answer using \columncolor from the xcolor package to work in this environment:

\documentclass{article}
\usepackage{amsmath}
\usepackage[table]{xcolor}
\usepackage{blkarray} % blockarrays; 

\begin{document}

\begin{align*}
\begin{blockarray}{ccc}
        \begin{block}{\BAmulticolumn{3}{>{}c}}
            \oint_{S^\textnormal{rec}}&\\
        \end{block}
        \begin{block}{(>{\scriptstyle}>{\columncolor{olive!20}}c>{\scriptstyle}c>{\scriptstyle}c)}
            a &\cdots & b\\
            \vdots&\ddots&\vdots\\
            cd &\cdots&N_\textnormal e\\
        \end{block}
\end{blockarray}
\end{align*}

\end{document}

It throws the following error message:

! Undefined control sequence.
\BA@.[10002,1]u ...\BA@bdollar \hfil \columncolor
{olive!20}\scriptstyle
l.19 \end{align*}

The second answer using the package hf-tikz and \tikzmark is also not solving the issue, as it fails for column entries of different lengths.

Can someone help me getting this to work in the \blockarray environment?

score 3 · Answer 1 · answered May 25 '18 at 19:22

I don't know how to solve the problem with \blockarray, but I think you can reach your desired result with a TikZ matrix of math nodes.

\documentclass{article}
\usepackage{amsmath}
\usepackage[table]{xcolor}
\usepackage{blkarray} % blockarrays; 

\usepackage{tikz}
\usetikzlibrary{matrix, positioning}

\begin{document}
\begin{tikzpicture}
    \node (A) {$\oint_{S^\textnormal{rec}}$};
    \matrix[
        below=-2pt of A,
        inner xsep=0pt,
        matrix of math nodes,
        nodes={
            text width=1.2em, 
            text height=1.4ex,
            text depth=.5ex, 
            align=center, 
            font=\scriptsize, 
        },
        left delimiter={(},right delimiter={)},
        column 1/.style={nodes={fill={olive!20}}}
        ] {
        a &[6pt]\cdots &[6pt] b\\
        \vdots&\ddots&\vdots\\[-4pt]
        cd &\cdots&N_\textnormal e\\
        };
\end{tikzpicture}
\end{document}

score 2 · Answer 2 · answered Aug 07 '23 at 08:06

A solution with {pNiceMatrix} of nicematrix.

\documentclass{article}
\usepackage{nicematrix}
\begin{document}
[\begin{pNiceMatrix}[first-row,margin]
  \Block{1-*}{\oint_{S^{\text{rec}}}} \
  \Block[fill=olive!20,rounded-corners]{3-1}{} a &  \cdots & b \
  \vdots & \ddots & \vdots \
  cd & \cdots & N_{\text{e}}
\end{pNiceMatrix}]
\end{document}

The same with the system of nicematrix for the dotted lines.

\documentclass{article}
\usepackage{nicematrix}
\begin{document}
[\begin{pNiceMatrix}[first-row,margin,xdots/shorten=2mm]
  \Block{1-*}{\oint_{S^{\text{rec}}}} \
  \Block[fill=olive!20,rounded-corners]{3-1}{} a &  \Cdots & b \
  \Vdots & \Ddots & \Vdots \
  cd & \Cdots & N_{\text{e}}
\end{pNiceMatrix}]
\end{document}

Coloring columns in blockarray

2 Answers2