如何标记 Tikz 包中的子图？

Question

使用该包制作带标签的子图有点棘手tikz。有人可以告诉我如何为每个子图提供自己的字母（A 代表左侧子图，B 代表中间子图，C 代表右侧子图）吗？代码如下：

\documentclass[aps,amsmath,amssymb,letter,scriptaddress,twocolumn, prl,showkeys]{revtex4}

\usepackage{amsmath}
\usepackage{amsthm}
\newtheorem{thm}{Theorem}
\usepackage{amssymb}
\usepackage{pgfplots}
\usepgfplotslibrary{groupplots}
\usepackage{mathtools}
\usepackage{makeidx}
\usepackage{amsfonts}
\usepackage[ansinew]{inputenc}
\usepackage[usenames,dvipsnames]{pstricks}
\usepackage{subfigure}
\usepackage{epsfig}
\usepackage{pst-grad} % For gradients
\usepackage{pst-plot} % For axes
\usepackage[colorlinks,hyperindex]{hyperref}
\makeatletter
\newcommand{\rmnum}[1]{\romannumeral #1}
\newcommand{\Rmnum}[1]{\expandafter\@slowromancap\romannumeral #1@}
\makeatother

\begin{document}

\begin{figure*}
    \begin{tikzpicture}[font=\footnotesize\sffamily]
      \begin{groupplot}[
         group style={group size=3 by 1,
    ylabels at=edge left
},
      view={0}{90},
      width=5cm,
      height=5cm,
      scale only axis,
      xmin=0, xmax=3,
      ymin=-8, ymax=0,
xlabel={x},
    ylabel={$y$},
      name=plot2,
      unbounded coords=jump]
    ]
    \nextgroupplot         
\addplot [only marks, mark=o, color=red] table{
1       -2.5
2       -3.3
3       -3.4
};
\addplot [domain=1:3, color=black] {-0.0538*x-2.8234};
        \nextgroupplot         
\addplot [only marks, mark=o, color=red] table{
1       -2.900422094
2       -3.244193633
3       -3.283414346
};
\addplot [domain=4:6, color=black] {-0.0333*x-3.1637};
        \nextgroupplot         
\addplot [only marks, mark=o, color=red] table{
4       -4.199705078
5       -4.674163057
6       -4.674163057
};
\addplot [domain=4:6, color=black] {-0.0749*x-1.7959};
 \end{groupplot}
    \end{tikzpicture}
\caption{My caption} 
 \label{myfig}
  \end{figure*}

\end{document}

Answer 1

这是一个解决方案（由于目前无法安装 revtex4，因此这里使用了 article cass）。应用了两种不同的标签技能。一种（自动标题，需要 alphalph 包）使用

\makeatletter
\pgfplotsset{
auto title/.style={title=(\AlphAlph{\pgfplots@group@current@plot})
    }
}
\makeatother

另一个（红色）用途

\node (A) at (group c1r1.north west) {A};  % c1r1 means column 1 row 1; 

锚点位置可以是，，，，north等等，等等southeastwest

代码

\documentclass[aps,amsmath,amssymb,letter,scriptaddress,twocolumn, prl,showkeys]{article}
\usepackage{amsmath}
\usepackage{amsthm}
\newtheorem{thm}{Theorem}
\usepackage{amssymb}
\usepackage{pgfplots,alphalph}
\usepgfplotslibrary{groupplots}
%\usepackage{mathtools}
%\usepackage{makeidx}
%\usepackage{amsfonts}
%\usepackage[ansinew]{inputenc}
%\usepackage[usenames,dvipsnames]{pstricks}
%\usepackage{subfigure}
%\usepackage{epsfig}
%\usepackage{pst-grad} % For gradients
%\usepackage{pst-plot} % For axes
%\usepackage[colorlinks,hyperindex]{hyperref}
\makeatletter
\newcommand{\rmnum}[1]{\romannumeral #1}
\newcommand{\Rmnum}[1]{\expandafter\@slowromancap\romannumeral #1@}
\makeatother

\makeatletter
\pgfplotsset{
auto title/.style={     title=(\AlphAlph{\pgfplots@group@current@plot})
    }
}
\makeatother

\begin{document}

\begin{figure*}
    \begin{tikzpicture}[font=\footnotesize\sffamily]
      \begin{groupplot}[
         group style={group size=3 by 1,
    ylabels at=edge left
},
      view={0}{90},
      width=5cm,
      height=5cm,
      scale only axis,
      xmin=0, xmax=3,
      ymin=-8, ymax=0,
xlabel={x},
    ylabel={$y$},
      name=plot2,
      unbounded coords=jump]
    ]
    \nextgroupplot [auto title]    
\addplot [only marks, mark=o, color=red,auto title] table{
1       -2.5
2       -3.3
3       -3.4
};
\addplot [domain=1:3, color=black,auto title] {-0.0538*x-2.8234};
        \nextgroupplot[auto title]         
\addplot [only marks, mark=o, color=red] table{
1       -2.900422094
2       -3.244193633
3       -3.283414346
};
\addplot [domain=4:6, color=black] {-0.0333*x-3.1637};
        \nextgroupplot[auto title]         
\addplot [only marks, mark=o, color=red] table{
4       -4.199705078
5       -4.674163057
6       -4.674163057
};
\addplot [domain=4:6, color=black] {-0.0749*x-1.7959};
 \end{groupplot}
    \node (A) at ([yshift=0.5cm]group c1r1.north west) {\color{red} A};
    \node (B) at ([yshift=0.5cm]group c2r1.north west) {\color{red} B};
    \node (C) at ([yshift=0.5cm]group c3r1.north west) {\color{red} C};
    \end{tikzpicture}
\caption{My caption} 
 \label{myfig}
  \end{figure*}

\end{document}