需要 tikz 的帮助

Question

如果有人能帮助我解决以下问题，我将不胜感激。这是我的乳胶代码：

\documentclass[12pt]{report}
\usepackage{caption}
\usepackage{subcaption}
\usepackage{tikz}
\usetikzlibrary{arrows}
\usepackage{verbatim}

\begin{document}

\tikzstyle{int}=[draw, line width = 1mm, minimum size=8em]


\begin{figure} 
\centering

\begin{tikzpicture}[node distance=4.5cm,auto,>=latex']
\node [int] (a) {};
\node (b) [left of=a,node distance=5cm, coordinate] {a};
\node [int] (c) [] {$S$};
\node [coordinate] (end) [right of=c, node distance=5cm]{};
\path[->] (b) edge node {$\gamma$} (a);
\draw[->] (c) edge node {$\psi$} (end) ;
\end{tikzpicture}
\caption{This is a single compartment model}

\end{figure}

\end{document}

我对 tikz 还很陌生，我曾简要地看过 Till Tantau 撰写的 405 页文档。我不得不说，我甚至不知道从哪里开始。上面的代码是一个模板，我设法对其进行了编辑，以生成所见的图像。我不太明白每个代码的作用，而且我确信这里有些代码是不需要的。我想引入一个循环，箭头位于框下方，指向框后方（箭头上有一个标签：“z”）。我还想知道是否有人可以帮助将箭头加粗，甚至更大。

或者，如果有人可以指导我阅读 tikz 文档中的哪一页来回答这些问题，我将不胜感激。

谢谢

Answer 1

你可以

1. 通过以下方式更改箭头的粗细ultra thick：

   \path[->, ultra thick, blue] (b) edge node {$\gamma$} (a);
   

   或指定实际的line width=：

   \draw[->, line width=5pt, red] (c) edge node {$\psi$} (end) ;
   

2. 使用语法绘制一个循环to（紫色箭头）：

   \draw [violet, ultra thick, ->] 
       ([xshift=-1.0cm]a.south) to[out=-120, in=-60, distance=2cm] ([xshift=1.0cm]a.south);
   

3. 添加节点\node：

   \node [below=0.5cm] at (a.south) {$z$};
   

笔记：

• 最好使用\tikzset而\tikzstyle不是应该使用 \tikzset 还是 \tikzstyle 来定义 TikZ 样式？。

代码：

\documentclass[12pt]{report}
\usepackage{caption}
\usepackage{tikz}
\usetikzlibrary{arrows}

\begin{document}

%\tikzstyle{int}=[draw, line width = 1mm, minimum size=8em]
\tikzset{int/.style={draw, line width = 1mm, minimum size=8em}}

\begin{figure} 
\centering

\begin{tikzpicture}[node distance=4.5cm,auto,>=latex']
\node [int] (a) {};
\node (b) [left of=a,node distance=5cm, coordinate] {a};
\node [int] (c) [] {$S$};
\node [coordinate] (end) [right of=c, node distance=5cm]{};
\path[->, ultra thick, blue] (b) edge node {$\gamma$} (a);
\draw[->, line width=5pt, red] (c) edge node {$\psi$} (end) ;

\draw [violet, ultra thick, ->] 
    ([xshift=-1.0cm]a.south) to[out=-120, in=-60, distance=2cm] ([xshift=1.0cm]a.south);
\node [below=0.5cm] at (a.south) {$z$};

\end{tikzpicture}
\caption{This is a single compartment model}

\end{figure}

\end{document}

Answer 2

Mike Renfro 的回答略有修改。添加了关于所用样式的评论，并使用了所有样式。

\documentclass[12pt]{report}
\usepackage{tikz}
\usetikzlibrary{arrows} % TikZ libraries needed for 
                        % drawing of TikZ pictures in document

\begin{document}
\begin{figure}
\centering
    \begin{tikzpicture}[% definition of own styles in picture 
    node distance = 5cm,% define distance between nodes and coordinates
    auto,               % placement od edge nodes
    >=latex',           % define type of arrow
       int/.style = {draw, line width = 1mm, minimum size=4em}
                        ]
\node[int]              (a) {This is a text};% make a box with style "int" 
                                             % containing a text "This is a text%}
\coordinate[left  of=a] (b);    % define just a point at node distance left from the box
\coordinate[right of=a] (c);    % similarly on the right side of the box
\path[->]   (b) edge node {$\gamma$}  (a)   % left arrow with label $\gamma$
            (a) edge node {$\psi$}    (c);  % right arrow
    \end{tikzpicture}

\caption{This is a single compartment model}
\end{figure}
\end{document}

对于使用 TikZ 绘图来说，阅读完整章节“TikZ ist kein Zeichenprogramm”非常有帮助。

Answer 3

不完全是一个答案，但是我从 MWE 中删除了冗余或无关的部分并添加了一些评论：

\documentclass[12pt]{report}
\usepackage{tikz}
\usetikzlibrary{arrows}

\begin{document}

% define a style for a node (thick lined box, square if any included label is small enough)
\tikzstyle{int}=[draw, line width = 1mm, minimum size=4em]

\begin{figure} 
\centering

\begin{tikzpicture}[node distance=4.5cm,auto,>=latex']
% make a thick lined box with a label
\node [int] (c) [] {This is a label};
% define a point to the left of the box, add a label for clarity, remove it when not needed
\node (b) [left of=c,node distance=5cm] {b};
% similarly, define a point to the right of the box
\node (end) [right of=c, node distance=5cm]{end};
% draw arrows from left to right, label them
\path[->] (b) edge node {$\gamma$} (c);
\path[->] (c) edge node {$\psi$} (end) ;
\end{tikzpicture}

\caption{This is a single compartment model}
\end{figure}

\end{document}

结果：