, how to express bar(zeta) in main title in boxplot

Hi everyone, I am plotting a boxplot with main title as main =
bquote(paste(.(ts.ind[s]), ": ", bar(zeta), " Boxplot from 2001 to 2009", sep = "")) but it doesn't work.  The program said they cannot find the function "bar".  Does anyone know how to do it correctly?  Thanks.

A reproducible example with the exact error message would
be good. Anyway, it seems pretty clear what you want and
one solution is to _not_ use 'main='. For base graphics,
I usually prefer to add titles with the title() function
which will work here.

a <- pi
boxplot(rnorm(200))
title(bquote(paste(.(a), ": ", bar(zeta),
       " Boxplot from 2001 to 2009", sep = "")))

It seems that setting main=<...> where <...> contains
bquote() works with plot(), but not with boxplot().

   -Peter Ehlers