如何在子图外设置图例？

Question

我正在制作一个包含三个子图的图形。然后我想在图形的左上角创建一个图例。目前，我在第三个子图中创建了图例，但最好将其放在图形本身的左上角。

感谢您提供的任何帮助:)

\begin{figure}[tbh]{
 \subfigure[]{         
  \begin{tikzpicture}
    \pgfplotsset{width = .3\textwidth, compat = newest}
    \begin{axis}[...]
        \addplot [...] file{...};
        \addplot [...] file{...};
    \end{axis}
\end{tikzpicture}}
\subfigure[]{         
  \begin{tikzpicture}
    \pgfplotsset{width = .3\textwidth, compat = newest}
    \begin{axis}[...]
        \addplot [...] file{...};
        \addplot [...] file{...};
    \end{axis}
\end{tikzpicture}}
\subfigure[]{         
  \begin{tikzpicture}
    \pgfplotsset{width = .3\textwidth, compat = newest}
    \begin{axis}[...]
        \addplot [...] file{...}; \addlengentry{a}
        \addplot [...] file{...}; \addlengentry{b} 
    \end{axis}
   \end{tikzpicture}}   
  \caption{...}
  \label{...}
  }
\end{figure}$

Answer 1

正如安德鲁在他的对你的问题发表评论一种解决方案是使用groupplots库pgfplots，我也在我的解决方案中介绍了它。但这种方法也可以适用于彼此相邻的三个法线轴环境。

此外，您只需在第一个图中添加一些虚拟线，这样您想要在图例中显示的所有条目都具有相同的样式，然后将相对于图的图例放在其顶部。

有关更多详细信息，请查看代码中的注释。

\documentclass[border=2mm]{standalone}
\usepackage{pgfplots}
    \usepgfplotslibrary{
        groupplots,
    }
    \pgfplotsset{
        compat=1.13,
        % define a style and put stuff in there which all plots have in common
        my style/.style={
            % reduce the `width' and `height' of the plots
            width=4cm,height=4cm,
            % set the labels for the axis
            xlabel=$x$,
            ylabel=$y$,
        },
        % define another style which contains the stuff of the legend
        my legend style/.style={
            legend entries={
                blue plot,
                red plot,
                green plot
            },
            legend style={
                at={([yshift=2pt]0,1)},
                anchor=south west,
            },
            legend columns=4,
        },
        % define a `cycle list` which will be used in the plots
        cycle multiindex* list={
            blue!75!black,
            red!75!black,
            green!75!black
                \nextlist
            mark=*,
            mark=square*,
            mark=triangle*
                \nextlist
        },
    }
\begin{document}
\begin{tikzpicture}
    % if the plots are very similar, use the `groupplots' axis environment
    \begin{groupplot}[
        group style={
            % place the three plots next to each other
            group size=3 by 1,
            % only set the tick and axis labels at the plots on the left
            % and on the bottom
            x descriptions at=edge bottom,
            y descriptions at=edge left,
        },
        % load the style created in the preamble
        my style,
        %
        % define the axis limits for the plots ...
        xmin=0,xmax=2,
        ymin=0,ymax=2,
        % ... and enlarge them a bit (use the default value)
        enlargelimits=true,
    ]
        \nextgroupplot[
            my legend style,
        ]
            \addplot coordinates {(0,0) (1,1) (2,2)};
            % to one of the plots you have to add some dummy plots
            % so they are collected/stored in the legend
            \addplot coordinates {(-1,-1)};
            \addplot coordinates {(-1,-1)};
        \nextgroupplot[
            % start with the second item of the `cycle list' here, so
            % shift it one element
            cycle list shift=1,
        ]
            \addplot coordinates {(0,2) (1,1) (2,0)};
        \nextgroupplot[
            % start with the third item of the `cycle list' here, so
            % shift it two elements
            cycle list shift=2,
        ]
            \addplot coordinates {(0,2) (1,1) (2,1)};
    \end{groupplot}
\end{tikzpicture}
\end{document}

Answer 2

• 简单来说，将\caption{}(和\label{})放在figure
  环境内部而不是内部，subfigure以将其与而
  figure不是相应的关联起来subfigure。（并使用
  \usepackage{subcaption}）
• 放在-s\caption{}之前
  subfigure以将其置于顶部。
• 
  \captionsetup{justification=raggedright,singlelinecheck=false}
  在之前使用\caption{}使其左对齐。（\usepackage{caption}）

我的 MWE：

\documentclass{article}

\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage[english]{babel}

\usepackage{caption}                %% to play with captions
\usepackage{subcaption}             %% for \begin{subfigure}
%\usepackage{tikz}              %% for tikz
\usepackage{pgfplots}               %% for \pgfplotsset

\begin{document}

\begin{figure}[tbh]             %% there is no {...
  \captionsetup{justification=raggedright,singlelinecheck=false}
  \caption{...}                 %% inside the figure not the subfigure
  \begin{subfigure}[b]{0.3\textwidth}       %% not \subfigure[]{...
    \includegraphics[width=0.15\textwidth]{solidtex.png}
  \end{subfigure}               %% not ...}
  \begin{subfigure}[b]{0.3\textwidth}       %% not \subfigure[]{...      
    \includegraphics[width=0.15\textwidth]{solidtex.png}
  \end{subfigure}               %% not ...}
  \begin{subfigure}[b]{0.3\textwidth}       %% not \subfigure[]{... 
     \includegraphics[width=0.15\textwidth]{solidtex.png}
  \end{subfigure}               %% not ...}
  \label{...}
\end{figure}

\end{document}