Two lines in an equation of one line

Question

What I want to do is to include two lines at the begging in an one-line equation, just like in the following picture.

enter image description here

Does anyone have any idea in order to achieve it? Thanks a lot.

\max requires amsmath. for a more general discussion of math operators, see newcommand vs. DeclareMathOperator. for a list of operators defined in this way, see the amsmath documentation -- texdoc amsmath on a tex live system. — barbara beeton, Apr 02 '14 at 13:32
Depending on how new you are to LaTeX, note that barbara's comment about amsmath means that you need \usepackage{amsmath} in the preamble of your document. — Steven B. Segletes, Apr 02 '14 at 13:34
@DavidCarlisle -- yup. correct. (i did try to check with grep but didn't search for the "correct" string.) even so, using amsmath if one has much math in a document isn't a bad idea. — barbara beeton, Apr 02 '14 at 13:57
@barbarabeeton yes agreed anyone typesetting math with latex should use amsmath, but, still I didn't use it below:-) — David Carlisle, Apr 02 '14 at 14:00
Possible duplicates: How to make expanding middle delimitors like in the braket package; How to automatically resize the vertical bar in a set comprehension? — Werner, Apr 02 '14 at 15:51
To elaborate on David's answer, you are not asking for two lines but for a subscript to max. — Andrew Swann, Apr 02 '14 at 17:54
@Werner Ehm, I don't think this question is about the vertical bar, but about the max with subscript. — Torbjørn T., Apr 02 '14 at 17:55

score 3 · Answer 1 · answered Apr 02 '14 at 13:52

3

enter image description here

Please always post a complete document not just a fragment:

\documentclass[12pt]{article}

\begin{document}


\[
\max_{x\in\mathcal{J}(k)}\left\{ \sum_a^b something \middle| something\right\}
\]

\end{document}

answered Apr 02 '14 at 13:52

David Carlisle

757,742

I'd say that the outer fences a excessively large and the \middle| needs spacing around it. My solution to a similar problem http://tex.stackexchange.com/a/167749/3929 – daleif Apr 02 '14 at 14:04
@daleif yes, agreed. and something shouldn't be set in math italic, but I decided not to address those here and concentrate on the question about the subscript to max. – David Carlisle Apr 02 '14 at 14:09

Bernard · Accepted Answer · 2014-04-02T15:54:26.213

Using mathtools (that loads amsmathanyway) and its DeclarePairedDelimiterX command, you can have a better spacing for |, and a better control on the size of the braces:

    \documentclass[12pt,a4paper,leqno]{article}

\usepackage[utf8]{inputenc}
\usepackage{amssymb, mathtools}
\usepackage{textcomp} 

\DeclarePairedDelimiterX{\set}[2]{\{}{\}}{#1 \delimsize\vert #2}
\newcommand*\Set[1]{\set*{#1}}
\DeclarePairedDelimiter\abs{\lvert}{\rvert}

\let\emptyset\varnothing    

\begin{document} 
\begin{align}
\tag*{With \texttt{\textbackslash Big}:}       &  \max_{\mathbf x \in \mathcal J(\mathbf K)}\!{\set[\Big]{\sum_{i\in I}\mathcal G_{i  \abs{C_i}}(\mathbf{\Pi}_i, y_i, \emptyset)}{(\mathbf\Pi, y_i)\in \mathcal N(\mathbf x_i)}} \\
\tag*{With \texttt{\textbackslash bigg}:}       & \max_{\mathbf x \in \mathcal J(\mathbf K)}\!{\set[\bigg]{\sum_{i\in I}\mathcal G_{i  \abs{C_i}}(\mathbf{\Pi}_i, y_i, \emptyset)}{(\mathbf\Pi, y_i)\in \mathcal N(\mathbf x_i)}}\\
\tag*{With an implicit \texttt{\textbackslash left}:}        & \max_{\mathbf x \in \mathcal J(\mathbf K)}\!{\Set{\sum_{i\in I}\mathcal G_{i  \abs{C_i}}(\mathbf{\Pi}_i, y_i, \emptyset)}{(\mathbf\Pi, y_i)\in \mathcal N(\mathbf x_i)}}
\end{align}

\end{document}

enter image description here

Two lines in an equation of one line

2 Answers2