Increase row height in align* cases environment

Question

I'm trying to use cases to present some equations with fractions, and finding that the lines are too compressed to be easily read. Is there a way to increase both the spacing between lines and the size of the typeset characters? The MWE is

\documentclass{article}
\usepackage{amsmath}
\begin{document}

\begin{align*}
A = \begin{cases}
\frac{B-.5b}{C-.5c} & \text{sometimes} \\
\frac{D-.3d}{E-.7e} & \text{other times}
\end{cases}
\end{align*}

\end{document}

which produces

squished text in align

You can manually increase the height by writing \\[2ex] for example. — A.Ellett, Dec 22 '14 at 17:53
If everyone keeps adding answers, there will be nobody left to vote! 8^) — Steven B. Segletes, Dec 22 '14 at 18:19

David Carlisle · Accepted Answer · 2014-12-22T19:12:24.233

10

mathtools extends amsmath with dcases:

enter image description here

\documentclass{article}
\usepackage{mathtools}
\begin{document}

\[
A = \begin{dcases}
\frac{B-.5b}{C-.5c} & \text{sometimes} \\
\frac{D-.3d}{E-.7e} & \text{other times}
\end{dcases}
\]

\end{document}

edited Dec 22 '14 at 19:12

answered Dec 22 '14 at 18:12

David Carlisle

757,742

1

I'd be tempted to add [1ex] of extra vertical space between the two lines. And I wouldn't use align* for the present case, since it features only one equation. – Mico Dec 22 '14 at 18:20
@Mico yes to both, I just wanted to highlight using dcases, perhaps the real example has more lines:-) (but it shouldn't use align unless there are some alignment points, I'll edit thanks – David Carlisle Dec 22 '14 at 19:12

score 4 · Answer 2 · edited Apr 13 '17 at 12:34

The following shows how you can replicate cases using an array:

enter image description here

\documentclass{article}
\usepackage{amsmath}
\begin{document}

\begin{align*}
  A = \begin{cases}
    \frac{B-.5b}{C-.5c} & \text{sometimes} \\
    \frac{D-.3d}{E-.7e} & \text{other times}
  \end{cases}
\end{align*}
\begin{align*}
  A &= \begin{cases}
    \frac{B-.5b}{C-.5c} & \text{sometimes} \\
    \frac{D-.3d}{E-.7e} & \text{other times}
  \end{cases} \\
  A &= \renewcommand{\arraystretch}{1.5}\left\{\begin{array}{@{}l@{\quad}l@{}}
    \frac{B-.5b}{C-.5c} & \text{sometimes} \\
    \frac{D-.3d}{E-.7e} & \text{other times}
  \end{array}\right.\kern-\nulldelimiterspace
\end{align*}

\end{document}

The first align* replicates your output, while the second align* includes the original cases plus an array implementation. When using an array, you can adjust \arraystretch to stretch out the "cases" construction vertically (similar to other suggestions in Column and row padding in tables).

Note that the default \arraystretch for cases under amsmath is 1.2, as depicted in the \env@cases definition (taken from amsmath.dtx`):

\def\env@cases{%
  \let\@ifnextchar\new@ifnextchar
  \left\lbrace
  \def\arraystretch{1.2}%
  \array{@{}l@{\quad}l@{}}%
}

Of course you could change this default 1.2 stretch factor to something larger, but my assumption is that you want only a specific instance of cases to be slightly aired out rather than make a global change.

The size of the characters can be adjusted by using \dfrac instead of \frac. However, this would require a larger \arraystretch than 1.5. I'm not sure what is to be gained by this visually.

Steven B. Segletes · Answer 3 · 2014-12-22T18:40:09.437

3

All that I did was to invoke \displaystyle for each line and to insert an extra blank line. EDITED (upon Werner's reminder) to use \dfrac instead of \displaystyle\frac, when the amsmath package is loaded.

\documentclass{article}
\usepackage{amsmath}
\begin{document}

\begin{align*}
A = \begin{cases}
\dfrac{B-.5b}{C-.5c} & \text{sometimes} \\
\\
\dfrac{D-.3d}{E-.7e} & \text{other times}
\end{cases}
\end{align*}

\end{document}

enter image description here

edited Dec 22 '14 at 18:40

answered Dec 22 '14 at 18:09

Steven B. Segletes

237,551

@Werner You are, of course, right. I had forgotten that I loaded amsmath. – Steven B. Segletes Dec 22 '14 at 18:38

Bernard · Answer 4 · 2016-09-15T16:32:16.927

Here are three ways:

– with the empheq package (it loads mathtools, which loads amsmath, so it's pointless to load any of these);

– with the cases* environment (defined in mathtools) and \dfrac;

– with the cases* environment and \mfrac (medium-sized fractions, ~80 % of \displaystyle), from nccmath.

Added: There's also David Carlisle's excellent suggestion of using dcases (or dcases*), rather than my second proposition.

  \documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage[overload]{empheq}

\usepackage{nccmath}

\begin{document}

\begin{alignat*}{2}[left = {A = \empheqlbrace}]
 & \frac{B-.5b}{C-.5c} &\quad & \text{sometimes} \\
 & \frac{D-.3d}{E-.7e} & & \text{other times}
\end{alignat*}

\begin{equation*}
  A = \begin{cases*}
     \dfrac{B-.5b}{C-.5c} & sometimes \\
\dfrac{D-.3d}{E-.7e} & other times
  \end{cases*}
\end{equation*}

\begin{equation*}
  A = \begin{cases*}
    \mfrac{B-.5b}{C-.5c} & sometimes \\
\mfrac{D-.3d}{E-.7e} & other times
  \end{cases*}
\end{equation*}

\end{document}

Note that cases* automatically sets the second column in text mode, so one doesn't have to use text{…}.

enter image description here

Thanks for pointing out about cases* and \text{}. Also note that cases* requires mathtools. — Yuri P., Sep 15 '16 at 10:46

score 2 · Answer 5 · answered Jun 02 '16 at 14:13

An addition to all answers above

A useful feature is to control the vertical distance between the equations of the cases, array, or similar environments. You can do that by writing \\[your distance with units] instead of simply \\. For example \\[1.5em]. It works also for negative spacing, e.g., \\[-0.5em]

In this minimal example I use \\[1.0em]

\documentclass{article}
\usepackage{amsmath}
\begin{document}

    \begin{align*}
        A = \begin{cases}
            \dfrac{B-.5b}{C-.5c} & \text{sometimes} \\[1.0em]
            \dfrac{D-.3d}{E-.7e} & \text{other times}
        \end{cases}
    \end{align*}

\end{document}

This code is Steven B. Segletes' modified. In my opinion, it looks nicer that just an extra empty line. ;)

Increase row height in align* cases environment

5 Answers5