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TikZ 绘图的精度

tag-icon • tag-icon tikz-pgf
TikZ 绘图的精度

为什么线条超出了横坐标轴（蓝色圆圈）？

   \documentclass[border=5mm]{standalone}
   \usepackage{pgfplots}
   \usepackage{amssymb}
   \begin{document}

   \pgfmathdeclarefunction{gauss}{1}{%
   \pgfmathparse{1/(sqrt(2*pi))*exp(-((#1)^2)/2)}%
     }

   \begin{tikzpicture}
   \begin{axis}[
   domain=-3:3,
   tickwidth=0.1cm,
   major tick style=black,
   axis lines=middle,
   axis line style =thick,
   axis line style={shorten >=-10pt, shorten <=-15pt},
   xlabel=$x$,ylabel=$y$,
   xtick={-2,...,2},ytick={0,0.1,0.2,0.3},
   xticklabels={,,,1,,,},
   yticklabels={,0.1,,},
   height=5cm, width=10cm,
   clip=false,
   axis on top,
   every axis x label/.style={
   at={(ticklabel* cs:1.03)},
   anchor=west},
   every axis y label/.style={
   at={(ticklabel* cs:1.1)},
   anchor=south},
   samples=1000,
   >=stealth,
   ]

  \pgfmathsetmacro\valueA{gauss(0.8)}
  \pgfmathsetmacro\valueB{gauss(-1.5)}
  \addplot [fill=orange!40, draw=none, domain=-1.5:0.8] {gauss(x)} \closedcycle;
  \draw [orange!80,thick] (axis cs:0.8,0) -- (axis cs:0.8,\valueA);
  \draw [orange!80,thick] (axis cs:-1.5,0) -- (axis cs:-1.5,\valueB);
  \addplot [ thick] {gauss(x)};
  \node[below,orange!80] at (axis cs:0.8,0){$b$};
  \node[below,orange!80] at (axis cs:-1.5,0){$a$};
  \node[below left] at (axis cs:0,0){$0$};
  \draw[orange,->](axis cs:2,0.4)--(axis cs:0.2,0.25);
  \draw[blue] (axis cs:0.8,0)  circle [radius=0.2cm];
  \draw[blue] (axis cs:-1.5,0)  circle [radius=0.2cm];
  \node[draw][orange,anchor=south west] at (axis cs:2,0.4)  {$P(a\leqslant X \leqslant b)$};
  \end{axis}
  \end{tikzpicture}
  \end{document}

在此处输入图片描述

答案1

您的问题是您的x轴没有经过原点(0,0)

要修复，只需设置ymin为0或更少。

输出

在此处输入图片描述

代码

\documentclass[border=5mm]{standalone}
\usepackage{pgfplots}
\usepackage{amssymb}
\begin{document}

\pgfmathdeclarefunction{gauss}{1}
{%
  \pgfmathparse{1/(sqrt(2*pi))*exp(-((#1)^2)/2)}%
}

\begin{tikzpicture}
  \begin{axis}
    [
      ymin=0, %%%%%%%%%%%%%%%%%%%%%%%%%%%  <--- just do this
      domain=-3:3,
      tickwidth=0.1cm,
      major tick style=black,
      axis lines=middle,
      axis line style =thick,
      axis line style={shorten >=-10pt, shorten <=-15pt},
      xlabel=$x$,ylabel=$y$,
      xtick={-2,...,2},ytick={0,0.1,0.2,0.3},
      xticklabels={,,,1,,,},
      yticklabels={,0.1,,},
      height=5cm, width=10cm,
      clip=false,
      axis on top,
      every axis x label/.style=
      {
        at={(ticklabel* cs:1.03)},
        anchor=west
      },
      every axis y label/.style=
      {
        at={(ticklabel* cs:1.1)},
        anchor=south
      },
      samples=100,
      >=stealth,
    ]

    \pgfmathsetmacro\valueA{gauss(0.8)}
    \pgfmathsetmacro\valueB{gauss(-1.5)}
    \addplot [fill=orange!40, draw=none, domain=-1.5:0.8] {gauss(x)} \closedcycle;
    \draw [orange!80,thick] (axis cs:0.8,0) -- (axis cs:0.8,\valueA);
    \draw [orange!80,thick] (axis cs:-1.5,0) -- (axis cs:-1.5,\valueB);
    \addplot [ thick] {gauss(x)};
    \node[below,orange!80] at (axis cs:0.8,0){$b$};
    \node[below,orange!80] at (axis cs:-1.5,0){$a$};
    \node[below left] at (axis cs:0,0){$0$};
    \draw[orange,->](axis cs:2,0.4)--(axis cs:0.2,0.25);
    \draw[blue] (axis cs:0.8,0)  circle [radius=0.2cm];
    \draw[blue] (axis cs:-1.5,0)  circle [radius=0.2cm];
    \node[draw][orange,anchor=south west] at (axis cs:2,0.4) {$P(a\leqslant X \leqslant b)$};
  \end{axis}
\end{tikzpicture}
\end{document}

干杯，

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