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TikZ 绘图：刻度线之间的括号

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TikZ 绘图：刻度线之间的括号

在刻度标记之间绘制括号的最佳方法是什么？在刻度标记处分配节点会很方便，这可行吗？

我现在所掌握的最佳放置方法是猜测并检查。

梅威瑟：

\documentclass{article}

\usepackage{tikz}
\usetikzlibrary{patterns,decorations.pathreplacing}
\usepackage{pgfplots}
\pgfplotsset{compat=1.10}

\begin{document}

\begin{tikzpicture}
\begin{axis}[
    axis x line = middle,
    axis y line = middle,
    xticklabels={}
    ]
\addplot [domain=-1:5] { -x * (x-4) };
\end{axis}
\draw [thick,decoration={brace,mirror},decorate] (1.2,3) -- (5.7,3) node[midway,below,yshift=-.1cm] {4};
\end{tikzpicture}

\end{document}

MWE图片

答案1

下面我提出三个层次的改进：

  1. 您可以在环境\draw内部移动axis并使用axis cs坐标系，该坐标系可以访问图的坐标；此外，您还可以使用选项raise来移动括号：

    \documentclass{article}
\usepackage{pgfplots}
\usetikzlibrary{patterns,decorations.pathreplacing}
\pgfplotsset{compat=1.10}

\begin{document}

\begin{tikzpicture}
\begin{axis}[
    axis x line = middle,
    axis y line = middle,
    xticklabels={}
    ]
\addplot [domain=-1:5] { -x * (x-4) };
\draw [thick,decoration={brace,mirror,raise=5pt},decorate] 
  (axis cs:0,0) --
    node[below=7pt] {4} 
  (axis cs:4,0);
\end{axis}
\end{tikzpicture}

\end{document}

    解决方案 1 的输出

  2. 您不必事先知道交点的坐标；您可以让intersections库为您进行计算：

    \documentclass{article}
\usepackage{pgfplots}
\usetikzlibrary{patterns,decorations.pathreplacing,intersections}
\pgfplotsset{compat=1.10}

\begin{document}

\begin{tikzpicture}
\begin{axis}[
    axis x line = middle,
    axis y line = middle,
    xticklabels={},
    samples=100
    ]
\addplot[name path=curve,domain=-1:5] { -x * (x-4) };
\addplot[name path=line,domain=-1:5,forget plot] {0};
\draw[
  name intersections={of=curve and line, by={a,b}},
  thick,
  decoration={brace,mirror,raise=5pt},decorate
] 
  (a) --
    node[below=7pt] {4} 
  (b);
\end{axis}
\end{tikzpicture}

\end{document}

  3. 最后，您还可以使用calc库和lengthconvert包，例如，长度（4）也会自动计算：

    \documentclass{article}
\usepackage{lengthconvert}
\usepackage{pgfplots}
\usetikzlibrary{patterns,decorations.pathreplacing,intersections,calc}
\pgfplotsset{compat=1.10}

\begin{document}

\begin{tikzpicture}
\begin{axis}[x=1cm,
    axis x line = middle,
    axis y line = middle,
    xticklabels={},
    samples=100
    ]
\addplot[name path=curve,domain=-1:5] { -x * (x-4) };
\addplot[name path=line,domain=-1:5,forget plot] {0};
\draw[
  name intersections={of=curve and line, by={a,b}},
  decoration={brace,mirror,raise=5pt},
  decorate
]
  let \p1 = ($ (a) - (b) $),
      \n2 = {veclen(\x1,\y1)}
  in
  (a) --
    node[below=7pt] {\Convert[precision=1,number-only=true]{\n2}} 
  (b);
\end{axis}
\end{tikzpicture}

\end{document}

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