add matrix demo

Signed-off-by: surenyi <surenyi82@163.com>

README.md

@@ -6,3 +6,11 @@
 
 ![fig_aa8](./images/fig_aa8.png)
 
+
+## matrix.tex
+
+\matrix command demo
+
+![matrix](./images/matrix.png)
+
+

matrix.tex

@@ -0,0 +1,47 @@
+\documentclass[border=1cm] {standalone}
+\usepackage{tikz}
+
+\usetikzlibrary {arrows,shapes.geometric}
+\begin{document}
+\begin{tikzpicture}
+  [auto,
+   decision/.style={diamond, draw=blue, thick, fill=blue!20,
+                    text width=4.5em,align=flush center,
+                    inner sep=1pt},
+   block/.style ={rectangle, draw=blue, thick, fill=blue!20,
+                    text width=5em,align=center, rounded corners,
+                    minimum height=4em},
+   line/.style ={draw, thick, -latex',shorten >=2pt},
+   cloud/.style ={draw=red, thick, ellipse,fill=red!20,
+                    minimum height=2em}]
+
+  \matrix [column sep=5mm,row sep=7mm]
+  {
+    % row 1
+      \node [cloud] (expert)   {expert}; &
+      \node [block] (init)     {initialize model}; &
+      \node [cloud] (system)   {system}; \\
+    % row 2
+      & \node [block] (identify) {identify candidate model}; & \\
+    % row 3
+      \node [block] (update)   {update model};  &
+      \node [block] (evaluate) {evaluate candidate models}; & \\
+    % row 4
+      & \node [decision] (decide) {is best candidate}; & \\
+    % row 5
+      & \node [block] (stop)      {stop}; & \\
+  };
+  \begin{scope}[every path/.style=line]
+    \path          (init)     -- (identify);
+    \path          (identify) -- (evaluate);
+    \path          (evaluate) -- (decide);
+    \path          (update)   |- (identify);
+    \path          (decide)   -| node [near start] {yes} (update);
+    \path          (decide)   -- node [midway] {no} (stop);
+    \path [dashed] (expert)   -- (init);
+    \path [dashed] (system)   -- (init);
+    \path [dashed] (system)   |- (evaluate);
+  \end{scope}
+\end{tikzpicture}
+\end{document}
+