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三角形内部的阴影

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三角形内部的阴影

A(1,1), B(2,2), C(1,3)尝试使用以下代码绘制由顶点三角形所包围的区域：

\documentclass{article}

\usepackage{pgfplots}
\usepackage{tikz}
\usepgfplotslibrary{fillbetween}

\begin{document}

 \begin{figure}[h]
  \begin{tikzpicture}
   \begin{axis}
    [xlabel=$x$, ylabel=$y$, axis lines=middle, xtick={6}, ytick={6}, no marks, axis equal, xmin=-1, xmax=4, ymin=-1, ymax=4, enlargelimits={upper=0.1}]

    \addplot[no markers,samples=51, thick, domain=1:3, variable=t]({1},{t});

    \addplot[no markers,samples=51, thick, domain=1:2, variable=t, name path=A]({t},{t});

    \addplot[no markers,samples=51, thick, domain=1:2, variable=t, name path=B]({t},{4-t});

    \addplot[gray!30,opacity=0.6] fill between[of=A and B, soft clip={domain=1:2}];

    \path node[below left] at (0,0) {$O$};
    \draw node[below left] at (1,0) {$1$};
    \draw node[below] at (2,0) {$2$};
    \draw node[left] at (0,1) {$1$};
    \draw node[left] at (0,2) {$2$};
    \draw node[left] at (0,3) {$3$};
    \draw node[below left] at (1,1) {$A$};
    \draw node[right] at (2,2) {$B$};
    \draw node[above] at (1,3) {$C$};

    \draw node[below right] at (1.5,2) {$D$};

    \draw node[right] at (1,-.8) {\footnotesize{$x=1$}};
    \draw[densely dotted,black]  (2,2) -- (3,3);
    \draw[densely dotted,black]  (2,2) -- (3,1);

    \draw node[right] at (3,3) {\footnotesize{$y=x$}};
    \draw node[right] at (3,1) {\footnotesize{$y=4-x$}};
  \end{axis}
 \end{tikzpicture}
 \end{figure}

\end{document}

我获得以下输出： 在此处输入图片描述

因此没有指出任何节点。我错在哪里？

答案1

与上一个问题不同，你遗漏了

\pgfplotsset{compat=1.15}

使用compat=1.11或更新版本，TikZ 命令（\draw，，）中的坐标被解释为轴坐标，但如果没有设置，或者设置或更低，\path则需要使用而不是如果您希望坐标获得相同。\nodecompat1.10(axis cs:0,0)(0,0)

在这种情况下，大多数节点都不需要，让我们pgfplots为 x 和 y 刻度制作标签。我认为将nodes 附加到\addplots 会更方便标签的顶点和虚线的函数标签。

其他一些小问题：为什么不使用\node而不是\draw node？ 并且\footnotesize不是一个接受参数的宏，它是一个影响同一组/环境中的以下文本的字体开关。因此，您将其用作\footnotesize text，而不是\footnotesize{text}，以限制其效果，使用{\footnotesize text}。

代码输出

\documentclass{article}

\usepackage{pgfplots}
\pgfplotsset{compat=1.15}
\usepgfplotslibrary{fillbetween}

\begin{document}
\begin{tikzpicture}
\begin{axis}[
  xlabel=$x$, ylabel=$y$,
  axis lines=middle,
  axis equal,
  xmin=-1, xmax=4,
  ymin=-1, ymax=4,
  enlargelimits={upper=0.1},
  % set the specific ticks you need
  xtick={2},
  ytick={1,2,3},
  no markers,
  % all straight lines, 2 samples is all you need
  samples=2,
  % sets the length of the ticks, i.e. the small lines
  tickwidth=0pt
]

    \addplot[thick, domain=1:3, variable=t] ({1},{t})
          node[below,pos=0] {$A$}
          node[above,pos=1] {$C$};

    \addplot[thick, domain=1:2, variable=t, name path=A]({t},{t})
          node[right] {$B$};

    \addplot[thick, domain=1:2, variable=t, name path=B]({t},{4-t});

    \addplot[gray!30,opacity=0.6] fill between[of=A and B, soft clip={domain=1:2}];

    \addplot[densely dotted, domain=2:3, variable=t]({t},{t})
          node[right,font=\footnotesize] {$y=x$};
    \addplot[densely dotted, domain=2:3, variable=t]({t},{4-t})
          node[right,font=\footnotesize] {$y=4-x$};

    \node[below left] at (0,0) {$O$};
    \node[below left] at (1,0) {$1$};
    \node[below left] at (1.5,2) {$D$};

    \draw [densely dotted] (0,2) -| (2,0);
    \draw [densely dotted] (0,3) -- (1,3);
    \draw [densely dotted] (0,1) -| (1,-0.5)
          node[right,font=\footnotesize] {$x=1  $};

\end{axis}
\end{tikzpicture}
\end{document}

答案2

添加\pgfplotsset{compat=1.15}代码

\documentclass{article}

\usepackage{pgfplots}
\usepackage{tikz}
\usepgfplotslibrary{fillbetween}
\pgfplotsset{compat=1.15}

\begin{document}

 \begin{figure}[h]
  \begin{tikzpicture}
   \begin{axis}
    [xlabel=$x$, ylabel=$y$, axis lines=middle, xtick={6}, ytick={6}, no marks, axis equal, xmin=-1, xmax=4, ymin=-1, ymax=4, enlargelimits={upper=0.1}]

    \addplot[no markers,samples=51, thick, domain=1:3, variable=t]({1},{t});

    \addplot[no markers,samples=51, thick, domain=1:2, variable=t, name path=A]({t},{t});

    \addplot[no markers,samples=51, thick, domain=1:2, variable=t, name path=B]({t},{4-t});

    \addplot[gray!30,opacity=0.6] fill between[of=A and B, soft clip={domain=1:2}];

    \path node[below left] at (0,0) {$O$};
    \draw node[below left] at (1,0) {$1$};
    \draw node[below] at (2,0) {$2$};
    \draw node[left] at (0,1) {$1$};
    \draw node[left] at (0,2) {$2$};
    \draw node[left] at (0,3) {$3$};
    \draw node[below left] at (1,1) {$A$};
    \draw node[right] at (2,2) {$B$};
    \draw node[above] at (1,3) {$C$};

    \draw node[below right] at (1,2) {$D$};

    \draw node[right] at (1,-.8) {\footnotesize{$x=1$}};
    \draw[densely dotted,black]  (2,2) -- (3,3);
    \draw[densely dotted,black]  (2,2) -- (3,1);

    \draw[densely dotted,black]  (1,1) -- (1,-1);
     \draw[densely dotted,black]  (2,2) -- (2,0);
     \draw[densely dotted,black]  (0,3) -- (1,3);
     \draw[densely dotted,black]  (0,2) -- (2,2);
     \draw[densely dotted,black]  (0,1) -- (1,1);

    \draw node[right] at (3,3) {\footnotesize{$y=x$}};
    \draw node[right] at (3,1) {\footnotesize{$y=4-x$}};
  \end{axis}
 \end{tikzpicture}
 \end{figure}

\end{document}

我获得了期望的输出： 在此处输入图片描述

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