[R] Adding per-panel text to panel strips in lattice xyplot

[Richard M. Heiberger]

Take a look at the xysplom function in package HH.
You can use it as a model for what you want.

tmp <- data.frame(x=rnorm(24),
                  y=rnorm(24),
                  a=factor(rep(letters[1:2],12)),
                  b=factor(rep(LETTERS[1:3], c(8,8,8))))
xysplom(y ~ x | a*b, data=tmp, corr=TRUE, layout=c(2,3))
 
The work is done with the cooperation of two functions.

xysplom.default looks for the corr argument and then creates
an additional conditioning factor and gives it a constant value.

strip.xysplom sees where it is and changes the strip label as needed.

strip.xysplom uses the R-2.3.1 technology for finding where it is.
Deepayan added some more functions in R-2.4.1, so that part of
the code can now be somewhat simplified.

lattice in R-2.4.0 also has a new strip.left argument (see ?xyplot and
serach for strip.left) that will allow you to put the additional
information in an additional left strip for each panel, rather than by making
changes to one of the standard top strips.

Rich