如何在表格中的两条水平线之间添加符号？

Question

我在两条水平线之间添加箭头符号时遇到了困难。我有代码来添加从一条水平线开始的箭头，但我不知道如何制作从中间开始的箭头。

我已附加一张图片来说明我想要达到的结果。

感谢@zarko，我已经获得了接近预期结果的代码，如下所示。

\begin{center}
    \begin{tikzpicture}[
        node distance = 3mm and 20mm,
        arr/.style = {draw=blue!70!black, -{Straight Barb[scale=0.8]}, very thick},
          N/.style = {font=\small, text width=60mm, align=center, inner sep=2pt},
                                ]
        % left image
        \node (n1) [N]  {Set \mbox{$r_1=0$}\\
                         Use fixed window $[0,r_2]$};
        \draw[thick]    (n1.west) -- ++ (0,-30mm)
                        (n1.east) -- ++ (0,-30mm);
                        %
        \coordinate[below=19mm of n1.west] (aux1);
        \path[arr]  (n1.east |- aux1) node[right] {$r_2$} --
                    (aux1) node[left] {$r_2$};
                    
        % right image
        \node (n2) [N, right=of n1]  
                        {Set \mbox{$r\in[0,r_1-r_2]$}\\
                         Anvend fast termineringsvindue $[r_1,r_2]$};
        \draw[thick]    (n2.west) -- ++ (0,-30mm)
                        (n2.east) -- ++ (0,-30mm);
        
                        %
        \coordinate[below=19mm of n2.west] (aux2);
        \coordinate[above=of aux2] (aux3);
        \coordinate[above=of aux3] (aux4);
        \coordinate[above=of aux4] (aux5);
        \path[arr]  (n2.east |- aux2) --
                    (aux2) node[left] {$r_1$};
        \path[arr]  (n2.east |- aux3) node[right] {$r_2$} -- ++ 
                    (-36mm,0) node[left] {$r_1$};
        \path[arr]  (n2.east |- aux4) -- node[above] {$r_w=r_2-r_1$} ++
                    (-24mm,0) node[left] {$r_1$};
                    
    \end{tikzpicture}
\end{center}

Answer 1

下面的内容应该能让你了解如何做到这一点。你可以让你的箭头从任意位置开始。只要你不使用--(或to)，\path就不会绘制任何内容（过于简单，但在这种情况下是正确的）。因此，你可以移动到特定点（例如，(aux1)移动到坐标aux1，并++(2,0)从当前位置向右移动两厘米），并在到达所需点后开始绘制。

\documentclass[tikz,border=3.14]{standalone}

\usetikzlibrary{positioning,arrows.meta}

\begin{document}
\begin{tikzpicture}[
    node distance = 3mm and 20mm,
    arr/.style = {draw=blue!70!black, -{Straight Barb[scale=0.8]}, very thick},
    N/.style = {font=\small, text width=60mm, align=center, inner sep=2pt},
  ]
  % left image
  \node (n1) [N]  {Set \mbox{$r_1=0$}\\
  Use fixed window $[0,r_2]$};
  \draw[thick]    (n1.west) -- ++ (0,-30mm)
  (n1.east) -- ++ (0,-30mm);
  %
  \coordinate[below=19mm of n1.west] (aux1);
  \path[arr]  (aux1) ++(2,0) node[right]{$r_2$} to (aux1);
  \coordinate[below=of aux1] (aux1);
  \path[arr]  (aux1) ++(4,0) node[right]{$r_2$} -- (aux1) node[left]{$r_1$};
  \coordinate[below=of aux1] (aux1);
  \path[arr]  (n1.east |- aux1) node[right] {$r_2$} -- (aux1);

  % right image
  \node (n2) [N, right=of n1]  
  {Set \mbox{$r\in[0,r_1-r_2]$}\\
  Anvend fast termineringsvindue $[r_1,r_2]$};
  \draw[thick]    (n2.west) -- ++ (0,-30mm)
  (n2.east) -- ++ (0,-30mm);

  %
  \coordinate[below=19mm of n2.west] (aux2);
  \coordinate[above=of aux2] (aux3);
  \coordinate[above=of aux3] (aux4);
  \coordinate[above=of aux4] (aux5);
  \path[arr]  (n2.east |- aux2) --
  (aux2) node[left] {$r_1$};
  \path[arr]  (n2.east |- aux3) node[right] {$r_2$} -- ++ 
  (-36mm,0) node[left] {$r_1$};
  \path[arr]  (n2.east |- aux4) -- node[above] {$r_w=r_2-r_1$} ++
  (-24mm,0) node[left] {$r_1$};

\end{tikzpicture}
\end{document}