\documentclass[a4paper]{article}
\usepackage{dottex}
\begin{document}
\def\dotwidth{.5\textwidth}
\begin{dotpic}
a -> b;
a -> c;
b -> d;
d -> a;
\end{dotpic}
\def\dotwidth{.8\textwidth}
\begin{neatopic}
a -- b;
b -- c;
a -- g;
e -- f;
g -- c;
\end{neatopic}
\end{document}