在高斯图中包括箭头

Question

我想复制这个数字

为此，我认为：

1. 绘制高斯，
2. 绘制箭头

这是我绘制左图的失败尝试：

\documentclass{article}
\usepackage{pgfplots}
\usepackage{tikz}
\usetikzlibrary {arrows.meta}
\usepackage{mathtools}
\begin{document}

% We define the function we are plotting here. Call it "Gauss"
\pgfmathdeclarefunction{gauss}{2}{%
  \pgfmathparse{1/(#2*sqrt(2*pi))*exp(-((x-#1)^2)/(2*#2^2))}%
}

% Begin plotting 
\begin{tikzpicture}
\begin{axis}[every axis plot post/.append style={mark=none,domain=-2:3,samples=50,smooth}, % All plots: from -2:2, 50 samples, smooth, no marks
  axis x line*=none, % no box around the plot, only x and y axis
  axis y line*=none, % the * suppresses the arrow tips
  axis line style={draw=none},
  dash pattern=on 4pt off 1pt on 4pt off 4pt,
  enlargelimits=upper] % extend the axes a bit to the right and top
  \addplot {gauss(0,0.5)};
  
\end{axis}
\end{tikzpicture}
\end{document}

我想添加箭头

\tikz{
\draw [-{Stealth[length=5mm]}] (0,0) -- (2,0);
}

但我不知道如何将其添加到图中。特别是如何确保箭头指向驼峰的顶峰。

Answer 1

这是一个lualatex使用内置的版本元帖子语言。

宏cutafter在这里派上用场了。您需要使用 编译此源lualatex。请点击上面的链接了解有关 Metapost 的更多信息。

\documentclass[border=5mm]{standalone}
\usepackage{luamplib}
\begin{document}
\mplibtextextlabel{enable}
\begin{mplibcode}
numeric _sqrtpp; _sqrtpp = 2.50662827463;  % sqrt(2pi)
vardef gauss(expr mu, sigma, x) = 
  if abs(x - mu) < 4 sigma:
    mexp(-128 * (((x - mu) / sigma) ** 2)) / _sqrtpp / sigma
  else: 
    0 
  fi 
enddef;
vardef gauss_curve(expr mu, sigma, a, b, s) = 
  (a, gauss(mu, sigma, a)) for x = a + s step s until b: .. (x, gauss(mu, sigma, x)) endfor
enddef;
vardef Z = gauss_curve(0, 1, -4, 4, 1/8) enddef;
vardef dotarrow(expr p) = image(drawarrow p; draw point 0 of p withpen pencircle scaled ahlength) enddef;

beginfig(1);
  numeric u; u = 21;
  path base, curve;
  base = (left -- right) scaled 5u;
  curve = Z xscaled u yscaled 8u;

  picture P[];
  P0 = image(draw base; draw up--down; draw curve dashed evenly scaled 1/2);
  P1 = image(
    draw P0;
    for x=-2, -1, 0, 1, 2:
      draw dotarrow((x*u, 0) -- (x*u, infinity) cutafter curve);
    endfor
  );
  P2 = image(
    draw P0;
    for x=-1.8, -0.6, 0.6, 1.8:
      draw dotarrow((x*u, 0) -- (x*u, infinity) cutafter curve);
    endfor
  );

  draw P1 shifted 120 left;
  draw P2 shifted 120 right;

endfig;
\end{mplibcode}
\end{document}