expressions and paste

I am trying to get a subscript into the title.
My expression is quote(bold(apoA[bold("1")]))
I have managed to get something near to what I want with

sd2 <-1.882
measure <- "g/L"
direction <- "increase"
chem <- quote(bold(apoA[bold("1")]))
plot(0,0)
  titletxt <- substitute(paste("per ", sd2, " ",measure," ", direction, "\n in usual ",chem),
   list(chem = chem,sd2=sd2,measure=measure,direction=direction))
  title(main=titletxt,cex.main=1.4,font.main=2)

However, I can't get bold text this way.

Emily.

On 11 Nov 2004 at 12:58, Roger D. Peng wrote:

Can you be a bit more specific?  Exactly what kind of symbol are you 
trying to put in the title?

-roger

Emily Baldock wrote:

I have written a function to plot data which will be used for various different chemistries.
A simplified version is:
plot_data <- function(risk,levels,chem,sd2,measure){
 plot(risk, levels,main=paste ("per", sd2, measure, "\n in usual", chem))
}
The problem is with the title.
This works fine if the variable "chem" is just text, but if it is an expression then obviously it won't work.
I have experimented with various things and I am at a complete loss for how to insert an expression into the middle of
a title. If the expression was going in directly I would use main=expression(paste("text ", expression, " text")) but
again this doesn't work. Can anyone help? thanks Emily.

-- 
Roger D. Peng
http://www.biostat.jhsph.edu/~rpeng/