% PSTricks: Figure 10.7, directed vs undirected chains
\documentclass{article}
\usepackage{com.braju.graphicalmodels}

\catcode`\@=11%

\pagestyle{empty}

\begin{document}
\TeXtoEPS

\LARGE
\psset{unit=10mm,arrowscale=1.5,linewidth=1.5pt}
\begin{pspicture}(0,0)(10,10)%\showgrid
  \SpecialCoor

   \rput(3,3){\GM@node[observed=false]{Y}} \GM@label[angle=90]{Y}{$Y$}

   \rput(1.5,1){\GM@node[observed=false]{X1}} \GM@label[angle=-90]{X1}{$X_1$}
   \rput(3,1){\GM@node[observed=false]{X2}} \GM@label[angle=-90]{X2}{$X_2$}
   \rput(4.5,1){\GM@node[observed=false]{Xd}} \GM@label[angle=-90]{Xd}{$X_d$}

   \ncline[arrows=->]{Y}{X1}
   \ncline[arrows=->]{Y}{X2}
   \ncline[arrows=->]{Y}{Xd}


   \rput(8,3){\GM@node[observed=false]{Yb}} \GM@label[angle=90]{Yb}{$Y$}

   \rput(6.5,1){\GM@node[observed=false]{X1b}} \GM@label[angle=-90]{X1b}{$X_1$}
   \rput(8,1){\GM@node[observed=false]{X2b}} \GM@label[angle=-90]{X2b}{$X_2$}
   \rput(9.5,1){\GM@node[observed=false]{Xdb}} \GM@label[angle=-90]{Xdb}{$X_d$}

   \ncline[arrows=-]{Yb}{X1b}
   \ncline[arrows=-]{Yb}{X2b}
   \ncline[arrows=-]{Yb}{Xdb}


\end{pspicture}

\endTeXtoEPS
\end{document}