我正在构建一个群图，其中的公共图例放置在图下的节点中。下面是一个重现我的问题的 MWE。
\documentclass{article}
\usepackage{pgfplots}
\usepgfplotslibrary{groupplots}
\usetikzlibrary{pgfplots.groupplots}
\pgfplotsset{compat = 1.12}
\begin{document}
\centering
\begin{figure}
\begin{tikzpicture}{fig3}
\begin{groupplot}[
legend columns=4,
legend entries={{\tiny Hold All},{\tiny Come and Go},{\tiny Random},{\tiny +Resources},{\tiny ++Resources},{\tiny ++ResourcesPT},{\tiny ++ResourcesSM},{\tiny ++ResourcesBM}},
legend to name=Fig3Legend,
group style={
group name = fig3_plots,
group size=3 by 1,
xlabels at=edge bottom,
ylabels at=edge left
},
width=\textwidth,
legend style={draw=none},
xlabel = {\footnotesize $\alpha$},
ylabel = {\footnotesize Avg Portfolio Value},
]
\nextgroupplot[title={\scriptsize +Resources},
y tick label style={
font=\tiny,
/pgf/number format/.cd,
fixed,
fixed zerofill,
precision=0,
/tikz/.cd
},
footnotesize,
x tick label style={
font=\tiny,
/pgf/number format/.cd,
fixed,
fixed zerofill,
precision=0,
/tikz/.cd
},
ymin=0,
xtick={1000,2000,3000,4000}]
\addplot+[black, mark=o,line join=round, mark repeat=50] table[col sep=comma, y=HoldAll, x=Alpha]{ElicitedFixedAlpha.csv};
\addplot+[black, mark=x,line join=round, mark repeat=50] table[col sep=comma, y=ComeAndGo, x=Alpha]{ElicitedFixedAlpha.csv};
\addplot+[black, mark=|,line join=round, mark repeat=50] table[col sep=comma, y=Random, x=Alpha]{ElicitedFixedAlpha.csv};
\addplot+[black, mark=square,line join=round, mark repeat=50] table[col sep=comma, y=Plus, x=Alpha]{ElicitedFixedAlpha.csv};
\nextgroupplot[title={\scriptsize ++Resources (Empirical CDF)},
y tick label style={
font=\tiny,
/pgf/number format/.cd,
fixed,
fixed zerofill,
precision=0,
/tikz/.cd
},
footnotesize,
x tick label style={
font=\tiny,
/pgf/number format/.cd,
fixed,
fixed zerofill,
precision=0,
/tikz/.cd
},
ymin=0]
\addplot+[black, mark=o,line join=round, mark repeat=50] table[col sep=comma, y=HoldAll, x=Alpha]{ElicitedFixedAlphaPlusPlus.csv};
\addplot+[black, mark=x,line join=round, mark repeat=50] table[col sep=comma, y=ComeAndGo, x=Alpha]{ElicitedFixedAlphaPlusPlus.csv};
\addplot+[black, mark=|,line join=round, mark repeat=50] table[col sep=comma, y=Random, x=Alpha]{ElicitedFixedAlphaPlusPlus.csv};
\addplot+[black, mark=square,line join=round, mark repeat=50] table[col sep=comma, y=PlusPlus, x=Alpha]{ElicitedFixedAlphaPlusPlus.csv};
\nextgroupplot[title={\scriptsize ++Resources (Elicited CDFs)},
y tick label style={
font=\tiny,
/pgf/number format/.cd,
fixed,
fixed zerofill,
precision=0,
/tikz/.cd
},
footnotesize,
x tick label style={
font=\tiny,
/pgf/number format/.cd,
fixed,
fixed zerofill,
precision=0,
/tikz/.cd
},
ymin=0]
\addplot+[black, mark=o,line join=round, mark repeat=50] table[col sep=comma, y=HoldAll, x=Alpha]{ElicitedFixedAlphaPlusPlus.csv};
\addplot+[black, mark=x,line join=round, mark repeat=50] table[col sep=comma, y=ComeAndGo, x=Alpha]{ElicitedFixedAlphaPlusPlus.csv};
\addplot+[black, mark=|,line join=round, mark repeat=50] table[col sep=comma, y=Random, x=Alpha]{ElicitedFixedAlphaPlusPlus.csv};
\addplot+[black, mark=triangle,line join=round, mark repeat=50] table[col sep=comma, y=PlusPlusPT, x=Alpha]{ElicitedFixedAlphaPlusPlus.csv};
\addplot+[black, mark=square,line join=round, mark repeat=50] table[col sep=comma, y=PlusPlusSM, x=Alpha]{ElicitedFixedAlphaPlusPlus.csv};
\addplot+[black, mark=asterisk,line join=round, mark repeat=50] table[col sep=comma, y=PlusPlusBM, x=Alpha]{ElicitedFixedAlphaPlusPlus.csv};
\end{groupplot}
\node (fig3_Legend) at ($(fig3_plots c2r1.center)-(0,2.5cm)$){\ref{Fig3Legend}};
\end{tikzpicture}
\caption{Fixed $\alpha$ Values}
\label{FixedAlphas}
\end{figure}
\end{document}
数据可从以下网址获取：
ElicitedFixedAlphaPlusPlus.txt
它产生以下输出
这很好，只是缺少最后两个图例条目。
在 groupplot 定义中我有
legend entries={{\tiny Hold All},{\tiny Come and Go},{\tiny Random},{\tiny +Resources},{\tiny ++Resources},{\tiny ++ResourcesPT},{\tiny ++ResourcesSM},{\tiny ++ResourcesBM}},
但正如您在图片中看到的，最后两个不在那里。相应的数据系列在图表中……很难看到，因为它们都在最右边的图表中彼此重叠，但它们在那里。那么为什么图例条目不显示呢？
答案1
您将在.log文件中发现警告
LaTeX Warning: Label `Fig3Legend' multiply defined.
LaTeX Warning: Label `Fig3Legend' multiply defined.
这意味着标签Fig3Legend应用于所有三个groupplots，因此\ref将仅指向其中最后一个，即最后一个groupplot。由于只有六个图，因此图例中会有六个条目。下面显示了一种解决方法。我首先为图定义了八种样式（为了方便起见，这不是必需的），然后在最后一个中groupplot添加了两个\addlegendimage，用于在图例中添加其他条目。
+Resources请注意，我还稍微改变了和的样式++Resources，这样混淆的可能性就更小了。您有三行具有相同的样式。
\documentclass[border=2mm]{standalone}
\usepackage{pgfplots}
\usepgfplotslibrary{groupplots}
\usetikzlibrary{pgfplots.groupplots}
\pgfplotsset{compat = 1.12}
\begin{document}
\begin{tikzpicture}[
HA/.style={black, mark=o,line join=round, mark repeat=50},
CAG/.style={black, mark=x,line join=round, mark repeat=50},
Rnd/.style={black, mark=|,line join=round, mark repeat=50},
P/.style={black, densely dashed, mark=square,line join=round, mark repeat=50},
PP/.style={black, thick, mark=square,line join=round, mark repeat=50},
PPPT/.style={black, mark=triangle,line join=round, mark repeat=50},
PPSM/.style={black, mark=square,line join=round, mark repeat=50},
PPBM/.style={black, mark=asterisk,line join=round, mark repeat=50}]
\begin{groupplot}[
legend columns=4,
legend style={nodes={font=\tiny}},
legend entries={Hold All,Come and Go,Random,+Resources,++Resources,++ResourcesPT,++ResourcesSM,++ResourcesBM},
legend to name=Fig3Legend,
group style={
group name = fig3_plots,
group size=3 by 1,
xlabels at=edge bottom,
ylabels at=edge left
},
width=\textwidth,
legend style={draw=none},
xlabel = {\footnotesize $\alpha$},
ylabel = {\footnotesize Avg Portfolio Value},
]
\nextgroupplot[title={\scriptsize +Resources},
y tick label style={
font=\tiny,
/pgf/number format/.cd,
fixed,
fixed zerofill,
precision=0,
/tikz/.cd
},
footnotesize,
x tick label style={
font=\tiny,
/pgf/number format/.cd,
fixed,
fixed zerofill,
precision=0,
/tikz/.cd
},
ymin=0,
xtick={1000,2000,3000,4000}]
\addplot+[HA] table[col sep=comma, y=HoldAll, x=Alpha]{ElicitedFixedAlpha.csv};
\addplot+[CAG] table[col sep=comma, y=ComeAndGo, x=Alpha]{ElicitedFixedAlpha.csv};
\addplot+[Rnd] table[col sep=comma, y=Random, x=Alpha]{ElicitedFixedAlpha.csv};
\addplot+[P] table[col sep=comma, y=Plus, x=Alpha]{ElicitedFixedAlpha.csv};
\nextgroupplot[title={\scriptsize ++Resources (Empirical CDF)},
y tick label style={
font=\tiny,
/pgf/number format/.cd,
fixed,
fixed zerofill,
precision=0,
/tikz/.cd
},
footnotesize,
x tick label style={
font=\tiny,
/pgf/number format/.cd,
fixed,
fixed zerofill,
precision=0,
/tikz/.cd
},
ymin=0]
\addplot+[HA] table[col sep=comma, y=HoldAll, x=Alpha]{ElicitedFixedAlphaPlusPlus.csv};
\addplot+[CAG] table[col sep=comma, y=ComeAndGo, x=Alpha]{ElicitedFixedAlphaPlusPlus.csv};
\addplot+[Rnd] table[col sep=comma, y=Random, x=Alpha]{ElicitedFixedAlphaPlusPlus.csv};
\addplot+[PP] table[col sep=comma, y=PlusPlus, x=Alpha]{ElicitedFixedAlphaPlusPlus.csv};
\nextgroupplot[title={\scriptsize ++Resources (Elicited CDFs)},
y tick label style={
font=\tiny,
/pgf/number format/.cd,
fixed,
fixed zerofill,
precision=0,
/tikz/.cd
},
footnotesize,
x tick label style={
font=\tiny,
/pgf/number format/.cd,
fixed,
fixed zerofill,
precision=0,
/tikz/.cd
},
ymin=0]
\addplot+[HA] table[col sep=comma, y=HoldAll, x=Alpha]{ElicitedFixedAlphaPlusPlus.csv};
\addplot+[CAG] table[col sep=comma, y=ComeAndGo, x=Alpha]{ElicitedFixedAlphaPlusPlus.csv};
\addplot+[Rnd] table[col sep=comma, y=Random, x=Alpha]{ElicitedFixedAlphaPlusPlus.csv};
\addlegendimage{P}
\addlegendimage{PP}
\addplot+[PPPT] table[col sep=comma, y=PlusPlusPT, x=Alpha]{ElicitedFixedAlphaPlusPlus.csv};
\addplot+[PPSM] table[col sep=comma, y=PlusPlusSM, x=Alpha]{ElicitedFixedAlphaPlusPlus.csv};
\addplot+[PPBM] table[col sep=comma, y=PlusPlusBM, x=Alpha]{ElicitedFixedAlphaPlusPlus.csv};
\end{groupplot}
\node (fig3_Legend) at ($(fig3_plots c2r1.center)-(0,2.5cm)$){\ref{Fig3Legend}};
\end{tikzpicture}
\end{document}