\begin{table}%t6
\caption{\label{tab6}Results of PCA for Sample~2.}
\small%\centering
\par
\begin{tabular}{cccc}\hline\hline
Set & Principal Component& Eigen value & Cumulative $\%$ \\
\hline
S1($R_{\rm gc},M_V,R_{\rm c}$)&1&1.4&47.7\\
 & 2&1.0&80.6 \\
 & 3& 0.6& 100.00\\\hline
S2($R_{\rm gc},M_V,c$)&1&1.3&44.5\\
 & 2& 1.0&78.2\\
 & 3& 0.7&100.00\\\hline
S3($R_{\rm gc},B-V,c$)& 1&1.5& 48.8\\
 & 2& 1.0& 81.8\\
 & 3& 0.5& 100.0\\\hline
S4($B-V,c,R_{\rm c}$)&1&2.1&71.0\\
 & 2&0.7&94.0\\
 &3&0.2&100.0\\\hline
S5($R_{\rm gc},M_V,c,R_{\rm c}$)& 1& 1.9&46.5\\
 & 2& 1.3& 79.9\\
 & 3& 0.6&96.3\\
 & 4& 0.2&100.0\\\hline
S6($M_V,c,R_{\rm c}$)&1&1.8&60.5\\
& 2&1.0&93.9\\
&3&0.2&100.0\\\hline
 S7([Fe/H], $c,R_{\rm c}$)&1&1.9&62.7\\
 & 2&1.0&94.4\\
 & 3&0.2&100.0\\\hline
\end{tabular}
\end{table}