figures

gistfile1.tex

\documentclass{standalone}% For the example only, any class will do

\usepackage{tikz}
\usetikzlibrary{positioning}% To get more advances positioning options
\usetikzlibrary{arrows}% To get more arrow heads

\begin{document}
\begin{tikzpicture}
  \node (A) {$A(i,j)$};
  \node (YI) [below of=A, left of=A]{$Y(i)$};
  \node (YJ) [below of=A, right of=A]{$Y(j)$};
  \node (XI) [above of=A, left of=A]{$X(i)$};
  \node (XJ) [above of=A, right of=A]{$X(j)$};
  \node (UI) [above of=XI, left of=XI]{$U_X(i)$};
  \node (UJ) [above of=XJ, right of=XJ] {$U_X(j)$};

  \draw[->] (UI) to node {} (XI);
  \draw[->] (UJ) to node {} (XJ);
  \draw[->] (XI) to node {} (A);
  \draw[->] (XJ) to node {} (A);
  \draw[->] (XI) to node {} (YI);
  \draw[->] (XJ) to node {} (YJ);
  \draw[->] (A) to node {} (YI);
  \draw[->] (A) to node {} (YJ);
  \draw[->, bend right] (UI) to node {} (YI);
  \draw[->, bend left] (UJ) to node {} (YJ);
\end{tikzpicture}

\begin{tikzpicture}
  \node (A) {$A(i,j)$};
  \node (YI) [below of=A, left of=A]{$Y(i)$};
  \node (YJ) [below of=A, right of=A]{$Y(j)$};
  \node (XI) [above of=A, left of=A]{$X(i)$};
  \node (XJ) [above of=A, right of=A]{$X(j)$};
  \node (UI) [above of=XI, left of=XI]{$U_X(i)$};
  \node (UJ) [above of=XJ, right of=XJ] {$U_X(j)$};

  \draw[->] (UI) to node {} (XI);
  \draw[->] (UJ) to node {} (XJ);
  \draw[->] (XI) to node {} (A);
  \draw[->] (XJ) to node {} (A);
  \draw[->] (XI) to node {} (YI);
  \draw[->] (XJ) to node {} (YJ);
  \draw[->] (A) to node {} (YI);
  \draw[->] (A) to node {} (YJ);
  \draw[->, bend right] (UI) to node {} (YI);
  \draw[->, bend left] (UJ) to node {} (YJ);
  \draw[->, bend left, color=orange] (UI) to node {} (A);
  \draw[->, bend right, color=orange] (UJ) to node {} (A);
\end{tikzpicture}
\end{document}