TikZ-based LaTeX code to create 3 basic DAGs in epidemiology/biostatistics.

Directed Acyclic Graphs in LaTeX using TikZ

\documentclass[]{article}
\usepackage{tikz}
\usetikzlibrary{positioning}

\begin{document}

%Graph 1
\begin{figure}
	\caption{Graph 1}
	\large{\begin{tikzpicture}[%
		->,
		>=stealth,
		node distance=1cm,
		pil/.style={
			->,
			thick,
			shorten =2pt,}
		]
		\node (1) {Y};
		\node[left=of 1] (2) {A};
		\node[right=of 1] (3) {L};
		\draw [->] (1.east) -- (3.west);
		\draw [->] (2) to [out=30, in=150] (3);
	\end{tikzpicture}}
\end{figure}

%Graph 2
\begin{figure}
	\caption{Graph 2}
	\large{\begin{tikzpicture}[%
		->,
		>=stealth,
		node distance=1cm,
		pil/.style={
			->,
			thick,
			shorten =2pt,}
		]
		\node (1) {L};
		\node[left=of 1] (2) {A};
		\node[below left=of 2] (3) {U};
		\node[right=of 1] (4) {Y};
		\draw [->] (2) to (1);
		\draw [->] (3) to (1);
		\draw [->] (3) to (4);
	\end{tikzpicture}}
\end{figure}

%Graph 3
\begin{figure}
	\caption{Graph 3}
	\large{\begin{tikzpicture}[%
		->,
		>=stealth,
		node distance=1cm,
		pil/.style={
			->,
			thick,
			shorten =2pt,}
		]
		\node (1) {Y};
		\node[left=of 1] (2) {A};
		\node[right=of 1] (3) {L};
		\node[rectangle, draw, right=of 3] (4) {C};
		\draw [->] (1) to (3);
		\draw [->] (3) to (4);
		\draw [->] (2) to [out=30, in=150] (3);
	\end{tikzpicture}}
\end{figure}


\end{document}