How to write conditional expression in LaTeX with text and math

Question

Being new in LaTeX I don't know where to look for the proper resources. I know this is probably documented for easily somewhere out there, but I'm struggling with knowing where to look - any help isappreciated.

How would you reproduce in LaTeX this conditional expression with one curly brace on the left side?

Hi @Iver, as a new user I recommend you reading some tips on how to ask a good question. There is more probability that you receive good answers and that your post will be useful for future users. Also try adding a mwe to your question. — GiuTeX, Apr 28 '21 at 11:21

Steven B. Segletes · Accepted Answer · 2021-04-28T22:56:10.007

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\[
  t(v) =
  \begin{cases}
    \text{John} & \text{hvis $v$ er variabelen $x$}\\
    \text{Paul} & \text{hvis $v$ er variabelen $y$}\\
    \text{George} & \text{hvis $v$ er variabelen $z$}\\
    \text{Yoko} & \text{ellers}
  \end{cases}
\]
\end{document}

Jendrik notes in the comments that the cases* environment, available with mathtools, sets the right-hand alignment automatically as text, rather than math, which is useful in this situation. Thus, the cases* equivalent of the above code would be

\documentclass{article}
\usepackage{mathtools}
\begin{document}
\[
  t(v) =
  \begin{cases*}
    \text{John} & hvis $v$ er variabelen $x$\\
    \text{Paul} & hvis $v$ er variabelen $y$\\
    \text{George} & hvis $v$ er variabelen $z$\\
    \text{Yoko} & ellers
  \end{cases*}
\]
\end{document}

Here's an alternative with tabstackengine, allowing the content to be set in text mode directly:

\documentclass{article}
\usepackage{tabstackengine}
\begin{document}
\[
  \setstackgap{L}{1.1\normalbaselineskip}% ROW BASELINESKIP
  \setstacktabbedgap{1em}% INTER-COLUMN GAP
  t(v) = \left\{
    \tabbedCenterstack[l]{% LEFT ALIGNED STACK CONTENT
    John & hvis $v$ er variabelen $x$\\
    Paul & hvis $v$ er variabelen $y$\\
    George & hvis $v$ er variabelen $z$\\
    Yoko & ellers
    }
  \right.
\]
\end{document}

I’d suggest using mathtools instead of amsmath (which is then loaded internally by mathtools), and then use cases* instead of cases. In this way, one doesn’t need to use\text{} in the second column. — Jendrik Stelzner, Apr 28 '21 at 22:30
@JendrikStelzner Thanks for the tip. I have added it to the answer. — Steven B. Segletes, Apr 28 '21 at 22:56

Bernard · Answer 2 · 2021-04-28T13:32:14.567

4

Another solution with just array and bigdelim:

\documentclass{article}
\usepackage{bigdelim, array}
\begin{document}
\begin{center}
  \sffamily
\begin{tabular}{l@{,}l@{\quad}l}
  \ldelim{{4}{*}[$t(v)={}$]
 & John & hvis $v$ er variabelen $x$ \
 & Paul & hvis $v$ er variabelen $y$ \
 & George & hvis $v$ er variabelen $z$ \
 & Yoko & ellers
\end{tabular}
\end{center}
\end{document}

edited Apr 28 '21 at 13:32

answered Apr 28 '21 at 12:48

Bernard

271,350

score 3 · Answer 3 · answered Apr 28 '21 at 11:38

Steven has already said enough, but just for completeness and for proving that LaTeX offers always new roads I'll post another solution by means of .., though I think cases environment is the most appropriate for this job.

\documentclass{article}
\usepackage{amsmath}


\begin{document}
    [
        t(v) = \left{\begin{array}{lr}
           \text{John} & \text{hvis $v$ er variabelen $x$}\
           \text{Paul} & \text{hvis $v$ er variabelen $y$}\
           \text{George} & \text{hvis $v$ er variabelen $z$}\
           \text{Yoko} & \text{ellers}
        \end{array}\right.
    ]
\end{document}

This produces

Notice that amsmath package is only needed for text command. A benefit from using array would be that you can control alignment by means of r and l (respectively right aligned, and left aligned) arguments in \begin{array}{lr}, and you can add lines as well as control manually spacing, by writing

\[
    t(v) = \left\{\begin{array}{l@{\hspace{3em}}|r}
        \text{John} & \text{hvis $v$ er variabelen $x$}\\
        \hline
        \text{Paul} & \text{hvis $v$ er variabelen $y$}\\
        \text{George} & \text{hvis $v$ er variabelen $z$}\\
        \text{Yoko} & \text{ellers}
    \end{array}\right.
\]

@{\hspace{3em}} can be set to whichever value in em, cm, pt and other measure you like for making custom space between columns, while | can be used for adding vertical lines bewreen the arry columns. Finally adding \hline you can achieve horizontal rules.

Little addendum: \left\{ and \right. fake the case behaviour of cases environment, so that if you prefer you can switch it to othe parenthesis, as [, (, \langle and so on.

How to write conditional expression in LaTeX with text and math

3 Answers3