[R] lattice: drawing strips for single-panel plots

[John G. Bullock]

The strip argument to panel.xyplot seems to be ignored for single-panel 
plots.  Here is an example:

   data(Chem97, package = "mlmRev")
   myStrip <- function(...) { ltext(.5, .5, 'strip text') }
   densityplot(~ gcsescore, data = Chem97, strip=myStrip)

The figure is printed with no strip.  The strip.default documentation 
suggests that Deepayan intended this behavior.  Still, it would help to 
be able to use the strip argument for single-panel plots.  Is there a 
simple way to do this?

Thank you,
John