LaTex折线图两个折线图在同一行展示

\begin{figure}[H]
     %图片1
     \begin{tikzpicture}[scale=0.8]%用scale调整图片大小
         \begin{axis}[
             xlabel=x in $m^2$,
             ylabel=y in $m^2$,
             tick align=outside,
             y tick label style={/pgf/number format/.cd,%
                 set thousands separator={}},
             width=3in,
             height=3in,
             legend style={at={(0.5,-0.2)},anchor=north}
             ]
         \addplot[smooth,mark=*,black] plot coordinates {
             (1999,1000)
             (2000,2000)
             (2001,3000)
             (2002,4000)
             (2003,5000)
             (2004,6000)
             };
     \addlegendentry{line}
     \label{figure 1}
     \end{axis}
     \end{tikzpicture}
     \qquad%两图片间填充空间
     %图片2
     \begin{tikzpicture}[scale=0.8]
         \begin{axis}[
             xlabel=x in $m^2$,
             ylabel=y in $m^2$,
             tick align=outside,
             y tick label style={/pgf/number format/.cd,%
                 set thousands separator={}},
             width=3in,
             height=3in,
             legend style={at={(0.5,-0.2)},anchor=north}
             ]
         \addplot[smooth,mark=*,black] plot coordinates {
             (1999,1000)
             (2000,2000)
             (2001,3000)
             (2002,4000)
             (2003,5000)
             (2004,6000)
         };
     \addlegendentry{line}
     \label{figure 2}
     \end{axis}
     \end{tikzpicture}\caption{two figures.\label{fig:two}}
\end{figure}