smoking-example-DAG.tex

\documentclass[tikz, border=2pt]{standalone}
% main document, called main.tex
\usepackage{tikz}
\begin{document}

\usetikzlibrary{fit,arrows,calc,positioning,shadows.blur}

\begin{tikzpicture}[var/.style={draw,circle,inner sep=0pt,minimum size=1.2cm}]
    % Nodes
    \node (A) [var] {$A$};
    \node (Y) [var, right=.8cm of A] {$Y$};
    \node (H) [var, above=.8cm of A] {$H$};
    \node (G) [var, above=.8cm of Y] {$G$};
    
    % Arrows
    \path[->, line width=0.5mm]
        (A) edge (Y)
        (H) edge (A)
        (H) edge (Y)
        (G) edge (Y);
\end{tikzpicture}

\end{document}