4

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

enter image description here

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

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  • You should never use eqnarray to begin with.
    – egreg
    Dec 22, 2021 at 11:23

2 Answers 2

5

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:

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

enter image description here

5

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} 

enter image description here

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

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