Use of the `\underbrace` in a `TikZ` environment

Question

The following code renders a graph of three vertices and three edges. (Nothing exciting.) Between the first vertex and the second vertex, I want to convey that there may be n - 1 more vertices. The second "displayed" vertex may actually be the nth vertex. I am getting error messages with my use of the \underbrace command. I am using it within a node command. I think this is allowed within a node command. Can \mathrlap be used within a node command? Should any of this be coded in math mode?

I may want to have a longer text under the brace - like "$n+1$ more vertices may be here but that is for me to know and you to find out." How would I typeset that on two or three lines?

In a graph, what is the convention regarding edges between consecutive "displayed" vertices when there may be more to the graph between them? Do I draw part of an edge off of each vertex? Do I typeset ellipses in the middle between the two "displayed" vertices? Do I typeset a pair of ellipses between the "displayed" vertices - one ellipses next to each vertex?

\documentclass{amsart}
\usepackage{amsmath}
\usepackage{mathtools} %Loads amsmath


\usepackage{tikz}
\usetikzlibrary{calc,intersections}


\begin{document}

\begin{tikzpicture}

\path (0,0) coordinate (vertex_1) (3,0) coordinate (vertex_n) (5,0) coordinate (vertex_n+1);
\draw[fill] (vertex_1) circle (1.5pt);
\draw[fill] (vertex_n) circle (1.5pt);
\draw[fill] (vertex_n+1) circle (1.5pt);

\draw (vertex_1) -- ($(vertex_1) +(0.75,0)$);
\draw (vertex_n) -- ($(vertex_n) +(-0.75,0)$) -- (vertex_n+1);

\coordinate (midpoint) at ($($(vertex_1) +(0.75,0)$)!0.5!($(vertex_n) +(-0.75,0)$)$);
\coordinate (brace) at ($(midpoint) +(0,-0.75)$);
%\node at (brace){\mathrlap{\underbrace{\phantom{n + 1\text{ more vertices}}}_{text}}};

\end{tikzpicture}


\end{document}

Answer 1

Between the first vertex and the second vertex, I want to convey that there may be n - 1 more vertices. The second "displayed" vertex may actually be the nth vertex. I am getting error messages with my use of the \underbrace command. I am using it within a node command. I think this is allowed within a node command. Can \mathrlap be used within a node command? Should any of this be coded in math mode?

You need to put \underbrace, etc. inside math mode for it to work (I don't know if this is the intended output)

\documentclass{amsart}
\usepackage{amsmath}
\usepackage{mathtools} %Loads amsmath
\usepackage{tikz}
\usetikzlibrary{calc,intersections}
\begin{document}
\begin{tikzpicture}
\path (0,0) coordinate (vertex_1) (3,0) coordinate (vertex_n) (5,0) coordinate (vertex_n+1);
\draw[fill] (vertex_1) circle (1.5pt);
\draw[fill] (vertex_n) circle (1.5pt);
\draw[fill] (vertex_n+1) circle (1.5pt);
\draw (vertex_1) -- ($(vertex_1) +(0.75,0)$);
\draw (vertex_n) -- ($(vertex_n) +(-0.75,0)$) -- (vertex_n+1);
\coordinate (midpoint) at ($($(vertex_1) +(0.75,0)$)!0.5!($(vertex_n) +(-0.75,0)$)$);
\coordinate (brace) at ($(midpoint) +(0,-0.75)$);
\node at (brace){$\mathrlap{\underbrace{\phantom{n + 1\text{ more vertices}}}_{text}}$};
\end{tikzpicture}
\end{document}

---

I may want to have a longer text under the brace - like "$n+1$ more vertices may be here but that is for me to know and you to find out." How would I typeset that on two or three lines?

My recommended version with automatic line breaks:

\documentclass[margin=2mm]{standalone}
\usepackage{tikz}
\usetikzlibrary{calc,intersections}
\begin{document}
\begin{tikzpicture}
\path (0,0) coordinate (vertex_1) (3,0) coordinate (vertex_n) (5,0) coordinate (vertex_n+1);
\draw[fill] (vertex_1) circle (1.5pt);
\draw[fill] (vertex_n) circle (1.5pt);
\draw[fill] (vertex_n+1) circle (1.5pt);
\draw (vertex_1) -- ($(vertex_1) +(0.75,0)$);
\draw (vertex_n) -- ($(vertex_n) +(-0.75,0)$) -- (vertex_n+1);
\coordinate (midpoint) at ($($(vertex_1) +(0.75,0)$)!0.5!($(vertex_n) +(-0.75,0)$)$);
\node (x) at (midpoint) {$\cdots$};
\node[draw,font=\footnotesize,text width=3cm] (callout) at (2,-2) {$n+1$ more vertices may be here but that is for me to know and you to find out.};
\draw[->] (callout) -- (x);
\end{tikzpicture}
\end{document}

or with manual line breaks:

\documentclass[margin=2mm]{standalone}
\usepackage{tikz}
\usetikzlibrary{calc,intersections}
\begin{document}
\begin{tikzpicture}
\path (0,0) coordinate (vertex_1) (3,0) coordinate (vertex_n) (5,0) coordinate (vertex_n+1);
\draw[fill] (vertex_1) circle (1.5pt);
\draw[fill] (vertex_n) circle (1.5pt);
\draw[fill] (vertex_n+1) circle (1.5pt);
\draw (vertex_1) -- ($(vertex_1) +(0.75,0)$);
\draw (vertex_n) -- ($(vertex_n) +(-0.75,0)$) -- (vertex_n+1);
\coordinate (midpoint) at ($($(vertex_1) +(0.75,0)$)!0.5!($(vertex_n) +(-0.75,0)$)$);
\node (x) at (midpoint) {$\cdots$};
\node[draw,font=\footnotesize,align=center] (callout) at (2,-2) {$n+1$ more vertices may\\be here but that is for me to\\know and you to find out.};
\draw[->] (callout) -- (x);
\end{tikzpicture}
\end{document}

---

In a graph, what is the convention regarding edges between consecutive "displayed" vertices when there may be more to the graph between them? Do I draw part of an edge off of each vertex? Do I typeset ellipses in the middle between the two "displayed" vertices? Do I typeset a pair of ellipses between the "displayed" vertices - one ellipses next to each vertex?

This question does not fall within the scope of TeX, LaTeX or related typesetting systems as defined in the help center.

Answer 2

\documentclass{amsart}
\usepackage{amsmath}
\usepackage{mathtools} %Loads amsmath


\usepackage{tikz}
\usetikzlibrary{calc,intersections}


\begin{document}

\begin{tikzpicture}

\path (0,0) coordinate (vertex_1) (3,0) coordinate (vertex_n) (5,0) coordinate (vertex_n+1);
\draw[fill] (vertex_1) circle (1.5pt);
\draw[fill] (vertex_n) circle (1.5pt);
\draw[fill] (vertex_n+1) circle (1.5pt);

\draw (vertex_1) -- ($(vertex_1) +(0.75,0)$);
\draw (vertex_n) -- ($(vertex_n) +(-0.75,0)$) -- (vertex_n+1);

\coordinate (midpoint) at ($(vertex_1)!0.5!(vertex_n)$);
\coordinate (center_of_brace) at ($(midpoint) +(0,-0.75)$);
\node[font=\footnotesize, anchor=north, inner sep=0, align=center] at (center_of_brace){\mbox{$n + 1$ more} \\
{\mbox{vertices}}};

\end{tikzpicture}

\end{document}