\begin{figure*}
%\centering  %图片全局居中
\subfigure[Span Length]{
%\subcaption*{your caption}
\label{Fig.sub.1}
\begin{tikzpicture}
  \begin{axis}[
    legend columns=-1,
    legend cell align=right,
    legend style={
    	draw=none,
	at={(-0.10, -0.30)}, 
	anchor=south west, 
	font=\scriptsize\bfseries,
    }, 
    %grid = both,
    ytick = {15,25, ..., 75},
    %ytick=\empty,
    ymax=80, ymin=15,
    ylabel = Exact \ \  F1 (\%),
    ylabel style = {yshift=-1.5em,font=\scriptsize\bfseries},
    y tick label style = {font=\scriptsize\bfseries},
    %axis x line=bottom,
    %axis y line=left,
    %enlargelimits=0.15,
    xtick = {0,1,2,3, 4},
    xticklabels = {,1-5,6-10,11-15, $\geq$ 16},
    xmax=4.2,xmin=0.8,
    x tick label style = {font=\scriptsize},
    width = 4.7cm,
	height = 5.4cm]
    %legend pos=north west,

\addplot[very thick, smooth, gray!80, mark = *, mark size = 2.0pt, mark options={fill=white}] coordinates
{ 
(1, 65.49)
(2, 43.23)
(3, 34.03)
(4, 19.19)
};
\addlegendentry{DepGCN}

\addplot[very thick, smooth, red!60, mark = halfdiamond*, mark size = 2.0pt, mark options={fill=white}] coordinates
{ 
(1, 67.89)
(2, 45.83)
(3, 32.57)
(4, 20.47)
};
\addlegendentry{DepHDN}

\addplot[very thick, smooth, a7c!70, mark = square, mark size = 2.0pt, mark options={fill=white}] coordinates
{ 
(1, 68.45)
(2, 48.11)
(3, 36.08)
(4, 25.59)
};
%\addlegendentry{P:comb}

\addplot[very thick, smooth, blue!70, mark = triangle, mark size = 2.0pt, mark options={fill=white}] coordinates
{ 
(1, 70.03)
(2, 50.16 )
(3, 41.69)	
(4, 30.20)
};
%\addlegendentry{M:comb}


%\legend{$l_1$,$l_2$,$l_3$}

\end{axis}
\end{tikzpicture}

}
\subfigure[Distance to Expression]{
\label{Fig.sub.2}
\begin{tikzpicture}
  \begin{axis}[
  %legend style={empty legend},
   legend columns=-2,
    legend cell align=right,
    legend style={
    			draw=none,
			at={(-0.05, -0.30)}, 
			anchor=south west, 
			font=\scriptsize\bfseries,
	}, %font=\ttfamily\itshape
    %grid = both,
    %ytick = {20,30, ..., 80},
    ytick=\empty,
    ymax=80, ymin=15,
    y tick label style = {font=\scriptsize\bfseries},
    %axis x line=bottom,
    %axis y line=left,
    %enlargelimits=0.15,
    xtick = {0,1,2,...,4},
    xticklabels = {,1-2,3-4,5-6, $\geq$ 7},
    xmax=4.2,xmin=0.8,
    x tick label style = {font=\scriptsize},
    width = 4.7cm,
	height = 5.4cm]
    %legend pos=north west,

\addplot[very thick, smooth, a7c!70, mark = square, mark size = 2.0pt, mark options={fill=white}] coordinates
{ 
(1, 71.88)
(2, 54.88 )
(3, 42.38)	
(4, 37.39)
};  
\addlegendentry{Comb}

\addplot[very thick, smooth, blue!70, mark = triangle, mark size = 2.0pt, mark options={fill=white}] coordinates
{ 

(1, 73.38)
(2, 55.30)
(3, 45.56)
(4, 41.76)
};
\addlegendentry{M-Comb}

\addplot[very thick, smooth, darkgray!60, mark = *, mark size = 2.0pt, mark options={fill=white}] coordinates
{ 
(1, 69.29)
(2, 52.86)
(3, 35.49)
(4, 32.88)
};
%\addlegendentry{P:GDN}

\addplot[very thick, smooth, red!60, mark = halfdiamond*, mark size = 2.0pt, mark options={fill=white}] coordinates
{ 
(1, 71.30)
(2, 53.50)
(3, 39.32)
(4, 34.94)
};
%\addlegendentry{P:Hidden}


\end{axis}
\end{tikzpicture}

}
\subfigure[Span Length]{
\label{Fig.sub.3}
\begin{tikzpicture}
  \begin{axis}[
    legend columns=-1,
    legend cell align=right,
    legend style={
    	draw=none,
	at={(-0.10, -0.30)}, 
	anchor=south west, 
	font=\scriptsize\bfseries,
    }, 
    %grid = both,
    ytick = {15,25, ..., 75},
    ytick=\empty,
    ymax=80, ymin=15,
    %ylabel = Exact  F1 (\%),
    %ylabel style ={yshift=-1.5em,font=\scriptsize\bfseries},
    %y tick label style = {font=\scriptsize\bfseries},
    %axis x line=bottom,
    %axis y line=left,
    %enlargelimits=0.15,
    xtick = {0,1,2,3, 4},
    xticklabels = {,1-5,6-10,11-15, $\geq$ 16},
    xmax=4.2,xmin=0.8,
    x tick label style = {font=\scriptsize},
    width = 4.7cm,
	height = 5.4cm]
    %legend pos=north west,

\addplot[very thick, smooth, gray!40, mark = pentagon, mark size = 2.0pt, mark options={fill=white}] coordinates
{ 
(1, 64.318)
(2, 42.368)
(3, 29.787)	
(4, 20.976)
};
\addlegendentry{Baseline}

\addplot[very thick, smooth, a10c, mark = otimes*, mark size = 2.0pt, mark options={fill=white}] coordinates
{ 
(1, 69.991)
(2, 49.127)
(3, 37.942)
(4, 26.601)
};
\addlegendentry{BERT}

\addplot[very thick, smooth, blue!70, mark = triangle, mark size = 2.0pt, mark options={fill=white}] coordinates
{ 
(1, 70.028)
(2, 50.160)
(3, 41.693)
(4, 30.198)
};
%\addlegendentry{+Syntax}

\addplot[very thick, smooth, black!60, mark = star, mark size = 3.0pt, mark options={fill=white}] coordinates
{ 
(1, 72.777)
(2, 54.037)
(3, 48.148)
(4, 36.044)
};
%\addlegendentry{+Both}

\end{axis}
\end{tikzpicture}
}
\subfigure[Distance to Expression]{
\label{Fig.sub.4}
\begin{tikzpicture}
  \begin{axis}[
  %legend style={empty legend},
   legend columns=-2,
   legend cell align=right,
   legend style={
    		draw=none,
			at={(-0.05, -0.30)}, 
			anchor=south west, 
			font=\scriptsize\bfseries,
	}, %font=\ttfamily\itshape
	%ytick = {20,30, ..., 80},
    %grid = both,
    %grid,
    ytick=\empty,
    ymax=80, ymin=15,
    y tick label style = {font=\scriptsize\bfseries},
    %axis x line=bottom,
    %axis y line=left,
    %enlargelimits=0.15,
    xtick = {0,1,2,...,4},
    xticklabels = {,1-2,3-4,5-6, $\geq$ 7},
    xmax=4.2,xmin=0.8,
    x tick label style = {font=\scriptsize},
    width = 4.7cm,
	height = 5.4cm]

\addplot[very thick, smooth, blue!70, mark = triangle, mark size = 2.0pt, mark options={fill=white}] coordinates
{ 
(1, 73.38)
(2, 55.30)
(3, 45.56)
(4, 41.76) 
};
\addlegendentry{M-Comb}

\addplot[very thick, smooth, black!60, mark = star, mark size = 3.0pt, mark options={fill=white}] coordinates
{ 
(1, 76.37)
(2, 61.38) 
(3, 48.78)
(4, 43.08)
};
\addlegendentry{Both}

\addplot[very thick, smooth, gray!40, mark = pentagon, mark size = 2.0pt, mark options={fill=white}] coordinates
{ 
(1, 68.20)
(2, 49.76) 	
(3, 34.10) 	
(4, 31.86)
};
%\addlegendentry{Baseline}

\addplot[very thick, smooth, a10c, mark = otimes*, mark size = 2.0pt, mark options={fill=white}] coordinates
{ 
(1, 73.38) 
(2, 57.90) 
(3, 43.54) 
(4, 38.78)
};
%\addlegendentry{+BERT}
\end{axis}
\end{tikzpicture}

}


\caption{Performance on predicting arguments with different span lengths and distances to the expressions.}
\label{fig:analysis_syn_bert}
\end{figure*}
