Can I make a matrix from just a parts of the cells?

Question

Can I make a matrix from just a parts of the cells?
i.e. not all the cells just some of it, like here:

It possible to make something like this?

Thank you!!

P.S. I'm using LyX.

Of course it is possible :-). At least drawing it as tikz picture or use package nicematrix, etc. What you try so far? — Zarko, Jul 27 '19 at 17:57
I'm using LyX - So I tried to put it at some cells and I didn't succeed this why I'm asking here... — heblyx, Jul 27 '19 at 17:58
blkarray perhaps (e.g. https://tex.stackexchange.com/questions/30791/array-with-labeling-columns/30792#30792, there are more examples on the site). You would have to write the code manually though, I don't think LyX has implemented support for blkarray. — Torbjørn T., Jul 27 '19 at 18:00
@Zarko, do you know how to write this array (above) at nicematrix? — heblyx, Jul 27 '19 at 18:07

score 7 · Accepted Answer · answered Jul 27 '19 at 18:11

The blkarray package makes it particularly easy:

\documentclass{article}
\usepackage{amsmath}
\usepackage{blkarray}

\begin{document}

\[
\begin{blockarray}{*{5}{c}} 
1 & 7 & 8 & 6 & 52 \\
\begin{block}{c[ccc]c}
3 & 17 & 9 & 9 & 1 \\
 12 & 10 & 9 & 6 & 5 \\
\end{block}
1 & 2 & 2 & 4 & 5
\end{blockarray}
\]

\end{document}

score 2 · Answer 2 · answered Apr 12 '21 at 11:06

You can easily do that with {bNiceMatrix} of nicematrix.

\documentclass{article}
\usepackage{nicematrix}
\begin{document}
$\begin{bNiceMatrix}[first-row,first-col,last-row,last-col]
1  & 7  & 8 & 6 & 52 \
3  & 17 & 9 & 9 & 1 \
12 & 10 & 9 & 6 & 5 \
1  & 2  & 2 & 4 & 5
\end{bNiceMatrix}$
\end{document}

With nicematrix, you have also tools to put delimiters exactly where you want.

\documentclass{article}
\usepackage{nicematrix}
\begin{document}
$\begin{NiceMatrix}
1  & 7  & 8 & 6 & 52 \
3  & 17 & 9 & 9 & 1 \
12 & 10 & 9 & 6 & 5 \
1  & 2  & 2 & 4 & 5
\CodeAfter
  \SubMatrix[{2-2}{3-3}]
\end{NiceMatrix}$
\end{document}

Can I make a matrix from just a parts of the cells?

2 Answers2