How to use strings from a data.frame as the argument of an expression() for plot

Thanks for your response; one more thing: Is it
possible to use a data.frame 
for the same effect, as these values are associated
with some others (I could 
of course use them separately, but merging them in a
data.frame should be 
possible in R)?

Try this:


e <- expression(O[3], NO, NO[2])
opar <- par(mfrow = c(2,2))
for(i in 1:3) plot(1, 1, type = "b", main =

bquote(.(e[[i]]) ~ Year ~

2005)) par(opar)

Also please read the last line to every post to

r-help and particularly

note the part about reproducible examples.   x and

y.were undefined.