Giving subset of equations big accolade

Question

I want to give a subset of equations, grouped together, in an eqnarray a big accolade to the right together with a short mathematical expression. What would be the best way to do so?

\begin{eqnarray*}
\sum_{k}x_{i - 11, k} + \dots + \sum_{k}x_{i - 2, k} &\ge& x_{i, 1}, \\
\sum_{k}x_{i - 1, k} &\le& 1 - x_{i, 1}, \\
\sum_{k}x_{i - 1, k} &\le& 1 - x_{i, 1},  \quad \quad   1 < i \le 11.
\end{eqnarray*}

An example of what I mean

If I should use something different to an eqnarray then I will do so.

You should never use eqnarray to begin with. – egreg Dec 22 '21 at 11:23 — egreg, Dec 22 '21 at 11:23

score 5 · Answer 1 · answered Dec 22 '21 at 12:37

You may use the IEEEeqnarraybox environment. See Appendix F of this article for more information about the environment.

\documentclass{article}
\usepackage{amsmath}
\usepackage{IEEEtrantools}
\begin{document}
    \begin{IEEEeqnarray}{rl}
        \begin{IEEEeqnarraybox}[\relax][c]{rCl}
        \sum_{k}x_{i - 11, k} + \dots + \sum_{k}x_{i - 2, k} & \ge & x_{i, 1}, \
        \sum_{k}x_{i - 1, k} & \le & 1 - x_{i, 1},\quad \quad
        \end{IEEEeqnarraybox} 
        & \Bigg} i > 11
         \
        \begin{IEEEeqnarraybox}{rCl}
        \sum_{k}x_{i - 1, k} & \le & 1 - x_{i, 1},\quad \quad
        \end{IEEEeqnarraybox} 
        & 1 < i \le 11.\
    \end{IEEEeqnarray}
\end{document}

The placement of the curly brace doesn't seem to be exactly in the center.

score 5 · Accepted Answer · answered Dec 22 '21 at 13:19

Never use eqnarray, see eqnarray vs align

You can use the very powerful nicematrix package instead:

\documentclass{article}
\usepackage{amsmath}
\usepackage{nicematrix}
\begin{document}
[
\newcolumntype{R}{>{\displaystyle}r}
\newcolumntype{L}{>{\displaystyle}l}
\begin{NiceArray}{@{} R<{{}} @{} LL}
\smash[t]{\vphantom{\bigg|}}
\sum_{k}x_{i - 11, k} + \dots + & \sum_{k}x_{i - 2, k} \ge x_{i, 1}, & \Block{2-1}{i>11} \
\vphantom{\bigg|}
&\sum_{k}x_{i - 1, k} \le 1 - x_{i, 1}, \
\smash[b]{\vphantom{\bigg|}}
&\sum_{k}x_{i - 1, k} \le 1 - x_{i, 1},  & 1 < i \le 11.
\CodeAfter\SubMatrix.{1-2}{2-2}}
\end{NiceArray}
]
\end{document}

The tricks are:

\vphantom{\bigg|} to ensure better spacing between rows; it's top- and bottom-smashed in the first and last;
\CodeAfter for the decoration;
\Block for the condition to be midway.

Giving subset of equations big accolade

2 Answers2