带有虚线端点的 PGFplots 中的绘图函数

Question

@Jasper Habicht 对这个问题的看法：使用 LaTeX 绘图

如何绘制函数，使得线的末端自动变成虚线，就像这张图一样（绿色和蓝色函数）：

Answer 1

\documentclass[tikz, border=1cm]{standalone}
\usepackage{pgfplots}
\pgfplotsset{compat=1.18}
\tikzset{
dotted ends/.style={
draw=none,
postaction={
   draw, decoration={lineto, 
   pre=moveto, pre length=0.05*\pgfmetadecoratedpathlength,
   post=moveto, post length=0.05*\pgfmetadecoratedpathlength, 
   }, decorate},
postaction={
   draw, dotted, decoration={lineto, 
   post=moveto, post length=0.95*\pgfmetadecoratedpathlength, 
   }, decorate},
postaction={
   draw, dotted, decoration={lineto, 
   pre=moveto, pre length=0.95*\pgfmetadecoratedpathlength,
   }, decorate},
}}
\begin{document}
\begin{tikzpicture}
\begin{axis}
\addplot[dotted ends, thick, blue, samples=50] {x^2};
\end{axis}
\end{tikzpicture}
\end{document}

遗憾的是，此解决方案不适用于该smooth选项。

编辑：现在使用固定长度（0.5 厘米）的虚线部分，可以更好地处理不同长度的图：

\documentclass[tikz, border=1cm]{standalone}
\usepackage{pgfplots}
\pgfplotsset{compat=1.18}
\tikzset{
dotted ends/.style={
draw=none,
postaction={
   draw, decoration={lineto, 
   pre=moveto, pre length=0.5cm,
   post=moveto, post length=0.5cm, 
   }, decorate},
postaction={
   draw, dotted, decoration={lineto, 
   post=moveto, post length=(\pgfmetadecoratedpathlength-0.5cm), 
   }, decorate},
postaction={
   draw, dotted, decoration={lineto, 
   pre=moveto, pre length=(\pgfmetadecoratedpathlength-0.5cm),
   }, decorate},
}}
\begin{document}
\begin{tikzpicture}
\begin{axis}
\addplot[dotted ends, thick, cyan, samples=500] {10+10*sin(500*x)};
\addplot[dotted ends, thick, blue, samples=50] {x^2};
\end{axis}
\end{tikzpicture}
\end{document}