\begin{tabular}{llll} 
\Rpackage{Matrix} & \Rpackage{lattice} & \Rpackage{mgcv} & \Rpackage{survival}\\ 
\Rpackage{KernSmooth} & \Rpackage{MASS} & \Rpackage{base} & \Rpackage{boot}\\ 
\Rpackage{class} & \Rpackage{cluster} & \Rpackage{codetools} & \Rpackage{compiler}\\ 
\Rpackage{datasets} & \Rpackage{foreign} & \Rpackage{grDevices} & \Rpackage{graphics}\\ 
\Rpackage{grid} & \Rpackage{methods} & \Rpackage{nlme} & \Rpackage{nnet}\\ 
\Rpackage{parallel} & \Rpackage{rpart} & \Rpackage{spatial} & \Rpackage{splines}\\ 
\Rpackage{stats} & \Rpackage{stats4} & \Rpackage{tcltk} & \Rpackage{tools}\\ 
\Rpackage{utils} &  &  & \\ 
\end{tabular}
