How to put braces over certain parts of matrices?

Question

I want to typeset something like this:

I couldn't find a way to achieve this using array or blkarray. Any help?

@TiMauzi I couldn't bring it to put brace over different columns of matrices. — Atom, Apr 01 '22 at 10:58
@Atom How about you just put the overbrace on top of the topmost row's values in your matrix? Meaning, you just put the overbrace IN the array, as well. — TiMauzi, Apr 01 '22 at 11:05

Sandy G · Accepted Answer · 2022-04-01T19:30:24.020

5

You can do this with the nicematrix package. Note that you must compile twice to get the result.

Note also that \OverBrace is a relatively new addition to nicematrix, so if you're using an old installation you'll have to update.

\documentclass{article}
\usepackage{nicematrix}
\begin{document}
[
m\begin{BNiceArray}{cccc|cc}[right-margin=.4em]
1 & 2 & 3 & 4 & 5 & 6 \
11 & 12 & 13 & 14 & 15 & 16 \
\CodeAfter
\SubMatrix[{1-3}{2-6}]
\OverBrace[shorten,yshift=3pt]{1-1}{2-2}{n}
\OverBrace[shorten,yshift=3pt]{1-3}{2-4}{r}
\OverBrace[shorten,yshift=3pt]{1-5}{2-6}{s}
\end{BNiceArray}n
]
\end{document}

edited Apr 01 '22 at 19:30

answered Apr 01 '22 at 19:25

Sandy G

42,558

Wow, that seems to be one impressively thoughtful package. The more you know... – TiMauzi Apr 01 '22 at 23:37

score 2 · Answer 2 · answered Apr 01 '22 at 11:18

2

Maybe something like this is what you are looking for:

\begin{array}{c}
  & n & & r & & s & \\
  m\,\big\lbrace & \overbrace{A} & \big[ & \overbrace{P} & \big\vert & \overbrace{Q} & \big] & \big\rbrace\,n
\end{array}

I think it could be made prettier (e.g. fixing some space widths and resizing the variables), but I think the overall idea should be clear.

answered Apr 01 '22 at 11:18

TiMauzi

841

That's a nice possibility! – Atom Apr 01 '22 at 12:18
@Atom If you prefer all the \overbraces to have the same height, just put them in an own row of your array and leave the braces empty. – TiMauzi Apr 01 '22 at 13:33
1

Somewhat related: https://tex.stackexchange.com/questions/59517/label-rows-of-a-matrix-by-characters – John Kormylo Apr 01 '22 at 14:13

How to put braces over certain parts of matrices?

2 Answers2

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