二叉树（格子）中间的垂直线

Question

这是一个非常棘手的问题，我不知道如何解决。我希望在二叉树的中间有一条虚线，下面有一个$\tau$……我想要的东西如下：

没有此行（或相关的 \tau）的图像代码如下：

 \documentclass{article}

 \usepackage{tikz}
 \usetikzlibrary{matrix,fit,backgrounds}



  \begin{document}


 \begin{tikzpicture}[>=stealth,sloped]
    \matrix (tree) [%
      matrix of nodes,
      minimum size=1cm,
      column sep=2.5cm,
      row sep=0.4cm,
    ]
    {  
              &                    &                     &  $_\tau S_0$             \\
              &                    &  $_{2\Delta t}S_0$  &                  \\
              & $_{\Delta t}S_0$   &                     &  $_\tau S_1$             \\
      $_0S_0$ &                    &  $_{2\Delta t}S_1$  &                  \\
              & $_{\Delta t}S_1$   &                      &  $_\tau S_2$         \\
              &                    &  $_{2\Delta t}S_2$  &                \\
              &                    &                     &  $_\tau S_3$    \\
    };

    \draw[->] (tree-4-1) -- (tree-3-2) node [midway,above] {$p$};
    \draw[->] (tree-4-1) -- (tree-5-2) node [midway,below] {$1-p$};
    \draw[->] (tree-3-2) -- (tree-2-3) node [midway,above] {};
    \draw[->] (tree-3-2) -- (tree-4-3) node [midway,below] {};
    \draw[->] (tree-5-2) -- (tree-4-3) node [midway,above] {};
    \draw[->] (tree-5-2) -- (tree-6-3) node [midway,below] {};

    \draw[->] (tree-2-3) -- (tree-1-4) node [midway,above] {};
    \draw[->] (tree-2-3) -- (tree-3-4) node [midway,below] {};
    \draw[->] (tree-4-3) -- (tree-3-4) node [midway,above] {};
    \draw[->] (tree-4-3) -- (tree-5-4) node [midway,below] {};
    \draw[->] (tree-6-3) -- (tree-5-4) node [midway,above] {};
    \draw[->] (tree-6-3) -- (tree-7-4) node [midway,below] {};

  \end{tikzpicture}

  \end{document}

Answer 1

该calc库使这成为一项简单的任务，但您必须为空矩阵单元分配名称：

\usetikzlibrary{calc}
\begin{tikzpicture}[>=stealth,sloped]
    \matrix (tree) [%
      matrix of nodes,
      minimum size=1cm,
      column sep=2.5cm,
      row sep=0.4cm,
    ]
    {  
              & |(top-left)|                   & |(top-right)|                     &  $_\tau S_0$             \\
              &                    &  $_{2\Delta t}S_0$  &                  \\
              & $_{\Delta t}S_0$   &                     &  $_\tau S_1$             \\
      $_0S_0$ &                    &  $_{2\Delta t}S_1$  &                  \\
              & $_{\Delta t}S_1$   &                      &  $_\tau S_2$         \\
              &                    &  $_{2\Delta t}S_2$  &                \\
              & |(bottom-left)|                   & |(bottom-right)|                    &  $_\tau S_3$    \\
    };

    \draw[->] (tree-4-1) -- (tree-3-2) node [midway,above] {$p$};
    \draw[->] (tree-4-1) -- (tree-5-2) node [midway,below] {$1-p$};
    \draw[->] (tree-3-2) -- (tree-2-3) node [midway,above] {};
    \draw[->] (tree-3-2) -- (tree-4-3) node [midway,below] {};
    \draw[->] (tree-5-2) -- (tree-4-3) node [midway,above] {};
    \draw[->] (tree-5-2) -- (tree-6-3) node [midway,below] {};

    \draw[->] (tree-2-3) -- (tree-1-4) node [midway,above] {};
    \draw[->] (tree-2-3) -- (tree-3-4) node [midway,below] {};
    \draw[->] (tree-4-3) -- (tree-3-4) node [midway,above] {};
    \draw[->] (tree-4-3) -- (tree-5-4) node [midway,below] {};
    \draw[->] (tree-6-3) -- (tree-5-4) node [midway,above] {};
    \draw[->] (tree-6-3) -- (tree-7-4) node [midway,below] {};

    % τ-line
    \draw[dashed] ($(top-left.north)!.5!(top-right.north)$) -- ($(bottom-left.south)!.5!(bottom-right.south)$);
    \node at ($(bottom-left.south)!.5!(bottom-right.south)-(0,1em)$) {$\tau$};

  \end{tikzpicture}

Answer 2

|-您可以通过和-|坐标限定符使用正交交叉。

\documentclass{article}

\usepackage{tikz}
\usetikzlibrary{matrix,fit,backgrounds}



\begin{document}


 \begin{tikzpicture}[>=stealth,sloped]
    \matrix (tree) [%
      matrix of nodes,
      minimum size=1cm,
      column sep=2.5cm,
      row sep=0.4cm,
    ]
    {  
              &                    &                     &  $_\tau S_0$             \\
              &                    &  $_{2\Delta t}S_0$  &                  \\
              & $_{\Delta t}S_0$   &                     &  $_\tau S_1$             \\
      $_0S_0$ &                    &  $_{2\Delta t}S_1$  &                  \\
              & $_{\Delta t}S_1$   &                      &  $_\tau S_2$         \\
              &                    &  $_{2\Delta t}S_2$  &                \\
              &                    &                     &  $_\tau S_3$    \\
    };

    \draw[->] (tree-4-1) -- (tree-3-2) node [midway,above] {$p$};
    \draw[->] (tree-4-1) -- (tree-5-2) node [midway,below] {$1-p$};
    \draw[->] (tree-3-2) -- (tree-2-3) node [midway,above] (a) {};
    \draw[->] (tree-3-2) -- (tree-4-3) node [midway,below] {};
    \draw[->] (tree-5-2) -- (tree-4-3) node [midway,above] {};
    \draw[->] (tree-5-2) -- (tree-6-3) node [midway,below] {};

    \draw[->] (tree-2-3) -- (tree-1-4) node [midway,above] {};
    \draw[->] (tree-2-3) -- (tree-3-4) node [midway,below] {};
    \draw[->] (tree-4-3) -- (tree-3-4) node [midway,above] {};
    \draw[->] (tree-4-3) -- (tree-5-4) node [midway,below] {};
    \draw[->] (tree-6-3) -- (tree-5-4) node [midway,above] {};
    \draw[->] (tree-6-3) -- (tree-7-4) node [midway,below] {};

\draw[dashed] (tree-7-4 -| a) -- (tree-1-4 -| a);
  \end{tikzpicture}

  \end{document}