# Force break-line to fit text in begin{cases}

I need to show an equation with begin{cases} however the text is bigger than the column of my article and I couldn't find a way to force it to break the line.

Code:

$Match_D = \begin{cases} 1, & \text{if D_j matches a single detected rectangle,} \\ 0, & \text{if D_j does not match any detected rectangle,} \\ f_{sc}(k) & \text{if D_j matches several (k) detected rectangles} \end{cases}$

$Match_G = \begin{cases} 1, & \text{if G_i matches a single detected rectangle,} \\ 0, & \text{if G_i does not match any detected rectangle,} \\ f_{sc}(k) & \text{if G_i matches several (k) detected rectangles} \end{cases}$


Regards

• You should input \mathit{Match} rather than Match: try it and see the difference. Or \mathrm{Match}, depending on your preferences. – egreg Jul 27 '18 at 21:58

You can use a \parbox of fixed width:

\documentclass{article}
\usepackage{amsmath}

\begin{document}
$Match_D = \begin{cases} 1, & \parbox{.3\linewidth}{if D_j matches a single detected rectangle,} \\[3ex] 0, & \parbox{.3\linewidth}{if D_j does not match any detected rectangle,} \\[3ex] f_{sc}(k) & \parbox{.3\linewidth}{if D_j matches several (k) detected rectangles} \end{cases}$

$Match_G = \begin{cases} 1, & \parbox[t]{.3\linewidth}{if G_i matches a single detected rectangle,} \\[3ex] 0, & \parbox[t]{.3\linewidth}{if G_i does not match any detected rectangle,} \\[3ex] f_{sc}(k) & \parbox[t]{.3\linewidth}{if G_i matches several (k) detected rectangles} \end{cases}$
\end{document}


You can use [t]op alignment (see Match_G) or (the default) [c]entered alignment (see Match_D).

Two variants without having to measure whatever: one with the empheqenvironment and tabulars, another with the cases* environment from mathtools. The first way enables you to easily number or subnumber each case if you wish. cases*is just a cases environment in which the 2nd column is automatically in text mode.

It require only loading empheq, which loads mathtools, which loads amsmath.

\documentclass{article}
\usepackage{empheq}

\begin{document}

\begin{subequations}
\begin{empheq}[left={\mathrm{Match}_G=\empheqlbrace}]{alignat=2}
if $G_i$ matches a single \\ detected rectangle,
\end{tabular} \\
& 0 & & \begin{tabular}[t]{l}
if $G_i$ does not match \\ any detected rectangle,
\end{tabular} \\
& f_{sc}(k) & & \begin{tabular}[t]{l}
if $G_i$ matches several \\ $(k)$ detected rectangle,
\end{tabular}
\end{empheq}
\end{subequations}

$\mathrm{Match}_G = \begin{cases*} 1, & if G_i matches a single \\[-0.5ex] & detected rectangle, \\%[0.5ex] 0, & if G_i does not match\\[-0.5ex] & any detected rectangle, \\%[0.5ex] f_{sc}(k) & if G_i matches several \\[-0.5ex] & (k) detected rectangles \end{cases*}$

\end{document}


• I believe this answer is correct too but I just tested the other – Claudio Jul 27 '18 at 23:31