custom strip in lattice ignoring plotmath expressions for all but style = 1 (PR#8733)

Full_Name: Ben Tyner
Version: 2.2.0
OS: i686-pc-linux-gnu
Submission from: (NULL) (128.210.141.240)


My appologies if this has already been fixed, but I didn't see it in the
tracking system yet so I thought I'd report it. Demonstration:

xyplot(Petal.Length ~ Petal.Width | Species, iris,
       strip = strip.custom(style = 1,
                            var.name = expression(beta),
                            strip.names = c(T, T)
               )
       ) # correct behavior w.r.t. var.name

xyplot(Petal.Length ~ Petal.Width | Species, iris,
       strip = strip.custom(style = 3,
                            var.name = expression(beta),
                            strip.names = c(T, T)
                            )
       ) # the var.name shows up as "beta"