Extend xyplot to superpose one or more symbols to each panel.
xyplot2(formula, data, type = "l", ...)a two-sided formula as accepted in xyplot
a list of data frames. Each component shall be able to evaluate the vatiables appearing in formula
a vector of characters to indicate what type of plots are to draw. Default is line.
any options as accepted in xyplot
On each panel, several plot types, the length of data, are superposed.