a string giving the name of the table. This
is used to name the layout viewport
heights
a unit vector giving the height of each
row
grobs
a single grob or a list of grobs
z
a numeric vector giving the order in which the
grobs should be plotted. Use Inf (the default) to
plot above or -Inf below all existing grobs. By
default positions are on the integers, giving plenty of
room to insert new