# splitting an equation inside curly brackets onto 2 lines without using \Big

I have a long equation:

\begin{equation} \begin{split}
X_{t} = mean(\left\{|Y_{t-4} - Z_{t-4}|,...,\\
|Y_{t+4} - Z_{t+4}|\right\})
\end{equation} \begin{split}


that I want to split over 2 lines and align as shown, but because it uses set notation and has small normal brackets outside the curly brackets, I don't want to use big curly brackets with the \bigg command when split over 2 lines. The \split command prevents me from using \left\ { and \right\ } with a line split. Is there a way of forcing small curly brackets with the split line command?

How I solved the problem:

This can be achieved by use of pseudo-parentheses:

 \begin{equation} \begin{split}
X_{t} = mean(\left\{&|Y_{t-4} - Z_{t-4}|,...,\right\.\\
&\left\.|Y_{t+4} - Z_{t+4}|\right\})
\end{equation} \end{split}


or better still as @Werner suggested, without the use of \right or \left:

\begin{equation} \begin{split}
X_{t} = mean(\{&|Y_{t-4} - Z_{t-4}|,...,\\
&|Y_{t+4} - Z_{t+4}|\})
\end{equation} \end{split}


I used the second option as it was simpler.

• Yes there is. Just use \{ and \}. No need for \left and \right here. – Werner Feb 17 '14 at 12:48
• @Werner - I don't have enough reputation points to upvote yet, but thanks for the answer! Also, just found a quick solution with \left and \right. You can terminate with pseudo-parenthesis \left\. and \right\. – user2524828 Feb 17 '14 at 12:50
• @user2524828 I don't think you should use \left and \right here, since this could lead to curly braces of different sizes. To illustrate try: \begin{equation} \begin{split} \left\{ a \right. & \\ & \left. \sum_{n=0}^{3} \right\} \end{split} \end{equation} – Morgan Sherman Feb 17 '14 at 20:29
• @MorganSherman - thanks for the tip. I discovered this yesterday when trying out the two options in my document, and decided to go with the \{ and \} options as you suggest. – user2524828 Feb 18 '14 at 16:44

You don't need \left and \right; your input has several mistakes, by the way: for instance \split{equation} means nothing (and it will produce errors). Also “mean” should be treated as an operator. I don't think the parentheses () around the set are useful.

With split you can choose the alignment point; here's a possibility:

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{equation}
\begin{split}
X_{t} = \operatorname{mean}(\{\,
&\lvert Y_{t-4} - Z_{t-4}\rvert,\dots,\\
&\lvert Y_{t+4} - Z_{t+4}\rvert\,\})
\end{split}
\end{equation}
\end{document} • Sorry that was a transcription error : I have used \begin{split} and \end{split}. Corrected in the question. Thanks for the tip re mean – user2524828 Feb 17 '14 at 14:31