How do I draw an ellipse around a term in an equation?

Question

I have seen how to draw a circle around a term in an equation (here). With the following code:

\makeatletter
\newcommand\mathcircled[1]{%
  \mathpalette\@mathcircled{#1}%
}
\newcommand\@mathcircled[2]{%
  \tikz[baseline=(math.base)] \node[draw,circle,inner sep=1pt, blue] (math) {$\m@th#1#2$};%
}
\makeatother
Needed assumptions on F, since we know $\lambda_1^*$ must lie within $0,1$ \
$\frac{b- \frac{F}{[\alpha(1-\gamma) - \gamma]}}{b-a} \leq 1 \iff b- \frac{F}{[\alpha(1-\gamma) - \gamma]} \leq b-a \iff \mathcircled{F \geq a \cdot [\alpha(1-\gamma) - \gamma]}$

I get this:

However, the result is aesthetically not satisfactory, since the term is quite long. I would like the circle/ellipse to rather adapt to the length of the term (just like the \boxed{} command of amsmath does for instance). E.g something like the following for my example in particular:

Use ellipse instead of circle? You need to \usetikzlibrary{shapes.geometric} — Rmano, Jul 13 '21 at 14:44
Tikz also supports ellipse. You might find https://tex.stackexchange.com/questions/399116/ideal-shape-of-elliptical-nodes useful. — John Kormylo, Jul 13 '21 at 14:46
Also look at https://tex.stackexchange.com/questions/570856/how-can-i-highlight-part-of-an-equation-with-tikz-but-without-extra-space-around (search for "tikz latex highlight formula" in google and you'll have plenty of them). — Rmano, Jul 13 '21 at 14:46
BTW, Welcome! Next time, please post minimal working example (MWE) to simplify the task of the answerer... — Rmano, Jul 13 '21 at 14:47
Do you want the ellipse to affect the spacing around the term, and if not should the ellipse be behind the text? — Andrew Stacey, Jul 13 '21 at 15:12

score 3 · Answer 1 · answered Jul 13 '21 at 14:53

Based on the solution you provide, why don't you use the shape library to draw an ellipse instead of a circle?

\documentclass{article}
\usepackage{mathtools}
\usepackage{tikz}
\usetikzlibrary{shapes}
\makeatletter
\newcommand\mathcircled[1]{%
  \mathpalette@mathcircled{#1}%
}
\newcommand@mathcircled[2]{%
  \tikz[baseline=(math.base)] \node[draw,ellipse,inner sep=1pt] (math) {$\m@th#1#2$};%
}
\makeatother
\begin{document}
[
  L(q+\varepsilon) = \mathcircled{L(q) + \varepsilon \frac{dL}{d\varepsilon}} + \cdots
]
\end{document}

Bernard · Accepted Answer · 2021-07-13T20:08:47.713

The circledsteps package (based on TiKZ) defines some rectangle with rounded smal sides for long terms.

However, if you really want an ellipse, pstricks defines a \psovalboxfor that:

\documentclass{article}
\usepackage{tikz}
\usepackage{circledsteps}
\usepackage{pstricks}
\begin{document}
Needed assumptions on F, since we know $\lambda_1^*$ must lie within $0,1$
[ \frac{b- \frac{F}{[\alpha(1-\gamma) - \gamma]}}{b-a} \leq 1 \iff b- \frac{F}{[\alpha(1-\gamma) - \gamma]} \leq b-a \iff \Circled[inner color=blue, outer color=blue]{F \geq a \cdot [\rule[-1.5ex]{0pt}{4ex}\alpha(1-\gamma) - \gamma]:} ]
[ \frac{b- \frac{F}{[\alpha(1-\gamma) - \gamma]}}{b-a} \leq 1 \iff b- \frac{F}{[\alpha(1-\gamma) - \gamma]} \leq b-a \iff \psovalbox[linecolor=blue, linewidth=0.5pt]{\color{blue} F \geq a \cdot [\rule[-1.5ex]{0pt}{4ex}\alpha(1-\gamma) - \gamma]} ]
\end{document}

How do I draw an ellipse around a term in an equation?

2 Answers2