expression below argmax

Question

In some places in my document I have used the following (and it works quite well):

\documentclass{article}
\usepackage{amsmath}
\DeclareMathOperator*{\argmax}{argmax} % thin space, limits underneath in displays

\begin{document}

\[z = \argmax_x f(x)\]

\end{document}

However, when I try to use something like this:

\documentclass{article}
\usepackage{amsmath}
\DeclareMathOperator*{\argmax}{argmax} % thin space, limits underneath in displays

\begin{document}

    \begin{tabular}{c l}
        $z = \argmax_x f(x)$ \\
        $z = \argmax_{x \in \mathcal{X}} f(x)$
    \end{tabular} 

\end{document}

It does not work anymore. It seems that tabular is somehow to blame here.

UPDATE2: Well, it was clearly because I was using inline math ($). Thanks David!

Answer 1

It isn't clear what you mean by "not work" the output is as I expect.

\documentclass{article}

\usepackage{amsmath}
\DeclareMathOperator*{\argmax}{argmax} % thin space, limits underneath in displays

\begin{document}



a
\[z = \argmax_x f(x)\]

b
\[z = \argmax_{x \in \mathcal{X}} f(x)\]

\end{document}

---

Updated question shows it is just an issue of display or inline setting:

\documentclass{article}

\usepackage{amsmath}
\DeclareMathOperator*{\argmax}{argmax} % thin space, limits underneath in displays

\begin{document}



a
\[z = \argmax_x f(x)\]

b
\[z = \argmax_{x \in \mathcal{X}} f(x)\]

a2
$z = \argmax_x f(x)$

b2
$z = \argmax_{x \in \mathcal{X}} f(x)$


a3 (don't do this)
$z = \argmax\limits_x f(x)$

b3 (or this)
$z = \argmax\limits_{x \in \mathcal{X}} f(x)$


c
\begin{align*}
z &= \argmax_x f(x)\\
z &= \argmax_{x \in \mathcal{X}} f(x)
\end{align*}




\end{document}

Answer 2

Try using \underset{belowtext}{text}.

Note below that:

• \mathrm is for using non-italics Roman font in math mode.
• \, is for adding a thin space

z = \underset{x}{\mathrm{argmax}}\, f(x)