par(ask=TRUE)

Hi,

1)
par(ask=TRUE)
histogram(~Y|F1 * F2 * F3,data = ...)

Successively displays many plots as the # of levels in F3 w/o asking for
input between each.
In other words I only get to see the plot for the last level. What's the
right commands?

library(grid)
?grid.prompt.

par() applies only to base graphics, and you are using grid 
(via lattice) here.

In 2.7.0 you will use devAskNewPage() instead, and this applies to the 
device and not the graphics subsystem.

2)
Also I am wondering if there are plot objects i.e. something like
obj<-plot(x,y)

Yes, in the lattice and ggplot[2] systems, and (in a different way) in teh 
grid graphics subsystem they are built on.

Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595