使用 LaTeX 中的 subcaption 包为子图创建通用图例

Question

我正在使用 LaTeX 模板，即 Elsivier 的 elsarticle 类，其中我使用 subcaption 包创建了两个子图。我遇到了这个答案它提供了一种为子图提供通用图例的解决方案，但它使用了 subfigure 包。不幸的是，我已经在草稿中为之前的图使用了 subcaption 包。

当我尝试将提供的代码集成到我的文档中时，遇到了如图所示的错误。

我怀疑这些错误可能源于 subfigure 和 subcaption 包之间的冲突。

我的主要问题是：在使用子标题包时，如何修改代码以使两个子图具有单个共同的图例？

以下是生成图形的代码片段：

\documentclass[preprint,3p,number]{elsarticle}

\usepackage{amssymb}
\usepackage[breaklinks=true,colorlinks,bookmarks=true]{hyperref}
\usepackage[inline]{enumitem}
\usepackage{times}
\usepackage{comment}
\usepackage{epsfig}
\usepackage{graphicx}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{algorithm}
\usepackage{algpseudocode}
\usepackage{tikz}
\usepackage{pgfplots}
\usepackage{enumitem}
\setitemize{noitemsep,topsep=0pt,parsep=0pt,partopsep=0pt}
\usepackage{subcaption}

\begin{document}

\begin{frontmatter}

%% Title, authors and addresses
\title{2 subfigures with 1 common legend}



\begin{abstract}

\end{abstract}



\begin{keyword}
% keywords here, in the form: keyword \sep keyword


\end{keyword}

\end{frontmatter}

%% main text

\begin{figure}[ht!]
\begin{subfigure}{0.48\textwidth}
\begin{tikzpicture}
\begin{axis}[
    ybar=0pt,
    enlargelimits=0.15,
    width=\columnwidth,
    ymin=90,
    ylabel={Accuracy (\%)},
    symbolic x coords={VGG,GoogLeNet,DenseNet,ResNet},
    xtick=data,
    bar width=10pt,
    legend style={ 
        at={(0.5,-0.15)},
        anchor=north,
        legend columns=-1,
    },
    axis x line*=bottom,
    axis y line*=left,
]
\addplot [blue, fill, opacity=0.7, nodes near coords,every node near coord/.append style={xshift=5pt,yshift=12pt,font=\footnotesize,rotate=90, opacity=1}]coordinates {(VGG, 93.86) (GoogLeNet, 95.22) (DenseNet, 94.85) (ResNet, 93.98)};
\addplot [green, fill, opacity=0.7, nodes near coords,every node near coord/.append style={xshift=5pt,yshift=12pt,font=\footnotesize,rotate=90, opacity=1}]coordinates {(VGG, 93.81) (GoogLeNet, 95.3) (DenseNet, 94.45) (ResNet, 93.97)};
\addplot [red, fill, opacity=0.7, nodes near coords,every node near coord/.append style={xshift=5pt,yshift=12pt,font=\footnotesize,rotate=90, opacity=1}]coordinates {(VGG, 93.86) (GoogLeNet, 95.09) (DenseNet, 94.53) (ResNet, 94.17)};
\legend{Cosine, Euclide, VBD}
\end{axis}
\end{tikzpicture}
\caption{CIFAR-10.}
\label{subfig:cifar10}
\end{subfigure}
%------------------------------------------------------------------------
\qquad
\begin{subfigure}{0.48\textwidth}
\begin{tikzpicture}
\begin{axis}[
    ybar=0pt,
    enlargelimits=0.15,
    width=\columnwidth,
    ymin=90,
    ylabel={Accuracy (\%)},
    symbolic x coords={VGG,GoogLeNet,DenseNet,ResNet},
    xtick=data,
    bar width=10pt,
    legend style={ 
        at={(0.5,-0.15)},
        anchor=north,
        legend columns=-1,
    },
    axis x line*=bottom,
    axis y line*=left,
]
\addplot [blue, fill, opacity=0.7, nodes near coords,every node near coord/.append style={xshift=5pt,yshift=12pt,font=\footnotesize,rotate=90, opacity=1}]coordinates {(VGG, 93.86) (GoogLeNet, 95.22) (DenseNet, 94.85) (ResNet, 93.98)};
\addplot [green, fill, opacity=0.7, nodes near coords,every node near coord/.append style={xshift=5pt,yshift=12pt,font=\footnotesize,rotate=90, opacity=1}]coordinates {(VGG, 93.81) (GoogLeNet, 95.3) (DenseNet, 94.45) (ResNet, 93.97)};
\addplot [red, fill, opacity=0.7, nodes near coords,every node near coord/.append style={xshift=5pt,yshift=12pt,font=\footnotesize,rotate=90, opacity=1}]coordinates {(VGG, 93.86) (GoogLeNet, 95.09) (DenseNet, 94.53) (ResNet, 94.17)};
\legend{Cosine, Euclide, VBD}
\end{axis}
\end{tikzpicture}
\caption{CIFAR-100.}
\label{subfig:cifar100}
\end{subfigure}
\caption{Ablation study on distance metrics.}
\label{fig:criteria_comparison}
\end{figure}

\end{document}

它生成了这个数字：

以下是一条链接进行复制。

我希望图例位于图形底部，两个子图之间。这是我使用 Paint 的预期输出：

我很感激任何帮助或建议。谢谢！

Answer 1

这个问题看起来不像是一个真正的subfigure问题，而是一个tikz/pgfplots问题。

新答案 根据pgfplots手册：

4.9.7 轴外的图例

您可以使用：

legend to name={<name>}

第一个选项中有图例axis，第二个选项中没有图例。此选项不绘制图例但存储其代码。

然后，当您使用时，将执行此代码\ref{<name>}。此命令甚至可以在任何命令之外使用tikzpicture，通常是在主figure命令之前\caption。

\centering在环境开始时使用命令figure使其居中，以及subfigures。

旧答案：

如果您不是绝对需要\ref单独使用 erCIFAR-10和CIFAR-100（使用例如\ref{fig:criteria_comparison}-left或-right），那么这是一个可能的解决方法：

1. 抑制sufigures 和subcaptions。
2. 将两个合并tikzpicture为一个，包含两个axis环境。
3. 将第二个放入合适的选项axis中scopexshift=...
4. 修改轴的锚点legend (at=...) in the first，并在第二个中抑制它。
5. 可选node，在相应的axis或中添加被抑制的子字幕作为 TikZ scope。

Answer 2

这是@Jhor 建议的一个可能的解决方案，如果有人需要代码，请发布：

\begin{figure}[ht!]
\centering
\begin{subfigure}{0.48\textwidth}
\begin{tikzpicture}
\begin{axis}[
    ybar=0pt,
    enlargelimits=0.15,
    width=\columnwidth,
    ymin=90,
    ylabel={Accuracy (\%)},
    symbolic x coords={VGG,GoogLeNet,DenseNet,ResNet},
    xtick=data,
    bar width=10pt,
    legend style={ 
        at={(0.5,-0.15)},
        anchor=north,
        legend columns=-1,
    },
    legend to name={mylegend},
    axis x line*=bottom,
    axis y line*=left,
]
\addplot [blue, fill, opacity=0.7, nodes near coords,every node near coord/.append style={xshift=5pt,yshift=12pt,font=\footnotesize,rotate=90, opacity=1}]coordinates {(VGG, 93.86) (GoogLeNet, 95.22) (DenseNet, 94.85) (ResNet, 93.98)};
\addplot [green, fill, opacity=0.7, nodes near coords,every node near coord/.append style={xshift=5pt,yshift=12pt,font=\footnotesize,rotate=90, opacity=1}]coordinates {(VGG, 93.81) (GoogLeNet, 95.3) (DenseNet, 94.45) (ResNet, 93.97)};
\addplot [red, fill, opacity=0.7, nodes near coords,every node near coord/.append style={xshift=5pt,yshift=12pt,font=\footnotesize,rotate=90, opacity=1}]coordinates {(VGG, 93.86) (GoogLeNet, 95.09) (DenseNet, 94.53) (ResNet, 94.17)};
\legend{Cosine, Euclide, VBD}
\end{axis}
\end{tikzpicture}
\caption{CIFAR-10.}
\label{subfig:cifar10}
\end{subfigure}
\hfill
%------------------------------------------------------------------------
\begin{subfigure}{0.48\textwidth}
\begin{tikzpicture}
\begin{axis}[
    ybar=0pt,
    enlargelimits=0.15,
    width=\columnwidth,
    ymin=90,
    ylabel={Accuracy (\%)},
    symbolic x coords={VGG,GoogLeNet,DenseNet,ResNet},
    xtick=data,
    bar width=10pt,
    legend style={ 
        at={(0.5,-0.15)},
        anchor=north,
        legend columns=-1,
    },
    axis x line*=bottom,
    axis y line*=left,
]
\addplot [blue, fill, opacity=0.7, nodes near coords,every node near coord/.append style={xshift=5pt,yshift=12pt,font=\footnotesize,rotate=90, opacity=1}]coordinates {(VGG, 93.86) (GoogLeNet, 95.22) (DenseNet, 94.85) (ResNet, 93.98)};
\addplot [green, fill, opacity=0.7, nodes near coords,every node near coord/.append style={xshift=5pt,yshift=12pt,font=\footnotesize,rotate=90, opacity=1}]coordinates {(VGG, 93.81) (GoogLeNet, 95.3) (DenseNet, 94.45) (ResNet, 93.97)};
\addplot [red, fill, opacity=0.7, nodes near coords,every node near coord/.append style={xshift=5pt,yshift=12pt,font=\footnotesize,rotate=90, opacity=1}]coordinates {(VGG, 93.86) (GoogLeNet, 95.09) (DenseNet, 94.53) (ResNet, 94.17)};
\end{axis}
\end{tikzpicture}
\caption{CIFAR-100.}
\label{subfig:cifar100}
\end{subfigure}
\ref{mylegend}
\caption{Ablation study on distance metrics.}
\label{fig:criteria_comparison}
\end{figure}