# [Tex/LaTex] Bipartite graphs

diagramsgraphs

I want to draw something similar to this in latex. How can I do it? I want it to be a directed graph and want to be able to label the vertices.

One option would be to use PGF/TikZ; the package is very well documented, and you'll find many examples in the documentation. Another source of examples can be found at TeXample.net

Here's a little example:

\documentclass{book}
\usepackage{tikz}
\usetikzlibrary{positioning,chains,fit,shapes,calc}

\begin{document}

\definecolor{myblue}{RGB}{80,80,160}
\definecolor{mygreen}{RGB}{80,160,80}

\begin{tikzpicture}[thick,
every node/.style={draw,circle},
fsnode/.style={fill=myblue},
ssnode/.style={fill=mygreen},
every fit/.style={ellipse,draw,inner sep=-2pt,text width=2cm},
->,shorten >= 3pt,shorten <= 3pt
]

% the vertices of U
\begin{scope}[start chain=going below,node distance=7mm]
\foreach \i in {1,2,...,5}
\node[fsnode,on chain] (f\i) [label=left: \i] {};
\end{scope}

% the vertices of V
\begin{scope}[xshift=4cm,yshift=-0.5cm,start chain=going below,node distance=7mm]
\foreach \i in {6,7,...,9}
\node[ssnode,on chain] (s\i) [label=right: \i] {};
\end{scope}

% the set U
\node [myblue,fit=(f1) (f5),label=above:$U$] {};
% the set V
\node [mygreen,fit=(s6) (s9),label=above:$V$] {};

% the edges
\draw (f1) -- (s6);
\draw (s6) -- (f2);
\draw (f2) -- (s7);
\draw (s7) -- (f3);
\draw (s8) -- (f3);
\draw (f3) -- (s9);
\draw (s9) -- (f5);
\draw (f5) -- (s6);
\end{tikzpicture}

\end{document}


EDIT: I add a variation of the previous graph (requested in a comment); each vertex will now be a labelled ordered pair. The idea is to use multiple variables in each \foreach construct; the first variable will be used to add a name to each node and to create the labels; the second and third variables will give the first and second coordinates of each ordered pair. The code:

\documentclass{book}
\usepackage{tikz}
\usetikzlibrary{positioning,chains,fit,shapes,calc}

\begin{document}

\definecolor{myblue}{RGB}{80,80,160}
\definecolor{mygreen}{RGB}{80,160,80}

\begin{tikzpicture}[thick,
fsnode/.style={},
ssnode/.style={},
every fit/.style={ellipse,draw,inner sep=5pt,text width=2cm},
->,shorten >= 3pt,shorten <= 3pt
]

% the vertices of U
\begin{scope}[start chain=going below,node distance=7mm]
\foreach \i/\xcoord/\ycoord in {1/6/8,2/5/1,3/-4/7,4/6/9,5/0/-3}
\node[fsnode,on chain,label=left:$t_{\i}$] (f\i) {$(\xcoord,\ycoord)$};
\end{scope}

% the vertices of V
\begin{scope}[xshift=4cm,yshift=-0.5cm,start chain=going below,node distance=7mm]
\foreach \i/\xcoord/\ycoord in {6/0/3,7/1/4,8/-2/1,9/5/9}
\node[ssnode,on chain,label=right:$t_{\i}$] (s\i) {$(\xcoord,\ycoord)$};
\end{scope}

% the set U
\node [myblue,fit=(f1) (f5),label=above:$U$] {};
% the set V
\node [mygreen,fit=(s6) (s9),label=above:$V$] {};

% the edges
\draw (f1) -- (s6);
\draw (s6) -- (f2);
\draw (f2) -- (s7);
\draw (s7) -- (f3);
\draw (s8) -- (f3);
\draw (f3) -- (s9);
\draw (s9) -- (f5);
\draw (f5) -- (s6);
\end{tikzpicture}

\end{document}