使用 Pgfplot 绘制的复现图

Question

我需要你的帮助，我必须重现这个图来解释峰值超阈值法（锅）使用 Pgfplot。谢谢您的回复。

Answer 1

这是一个例子。代码包含几条注释，但如果有任何不清楚的地方，请询问。

\documentclass[border=5mm]{standalone}
\usepackage{pgfplotstable} % also loads pgfplots

% make a table containing y-values and labels for (some of) the data points
\pgfplotstableread[col sep=comma]{
y,label
8,$Y_{1}$
2,
5.6,$Y_{2}$
5,$Y_{3}$
6,
4,
9,$Y_{j}$
10,
4,
}\mydata

\begin{document}
\begin{tikzpicture}
\begin{axis}[
  % 
  axis lines=middle,
  % labels for axes
  ylabel={$X_i$},
  xlabel={$i$},
  % set axes limits
  ymin=0,
  xmin=0,
  xmax=9.9,
  % define where to place ticks on the axes
  % and what text labels to use for the ticks
  ytick={4.5},
  yticklabels={$u$},
  xtick={1,2,3,9},
  xticklabels={$1$,$2$,$3$,$n$},
  tickwidth=0pt,
  % turn on grid lines for ticks on the y-axis
  ymajorgrids,
  % set the style of the single grid line
  grid style={densely dotted, gray}
]

\addplot [
   % comb plots are lines from the axis to the point
   ycomb,
   thick,
   % nodes near coords is for adding automatic labels at data points
   nodes near coords,
   % set the style of those nodes
   nodes near coords style={font=\small},
   % the following states that the text used for the labels should
   % be given explicitly in the data stream
   % symbolic means that it should not be parsed as a number
   point meta=explicit symbolic
 ]
 table[
    % define the x-coordinate
    x expr=\coordindex+1,
    % get y-values from the column named y in the table
    y=y,
    % get the data for the point labels from the column named label
    meta=label
  ] {\mydata};

\addplot [
   ycomb,
   thick,
   gray
 ]
 table[
    x expr=\coordindex+1,
    % the y-coordinate is defined  by the given calculation, i.e.
    % the smallest value of the y-value from the table and 4.5
    y expr={min(\thisrow{y}, 4.5)}
  ] {\mydata};

\end{axis}
\end{tikzpicture}

\end{document}