[R] How to pass a character argument which contains expressions to arg.names in barplot?

[jcano]

Hi all

Can anybody help me with this? I am trying to include in an automatic way
the argument in arg.names in a barplot. I generate the labels I want to
appear below the bars with a for loop, and they contain subscripts, so I
need to use expression

  anch<-0.05
  esp<-4
  for (i in 1:dim(Ntot)[1])
    {
    naux<-Ntot[i,]
    naux2<-naux[naux>0]
    nind<-which(naux>0)
    tit4<-character(0)
    for (j in 1:length(nind))
      {
      tit4<-c(tit4,paste("expression(n[paste[",i,",",nind[j],"])",sep=""))
      }
    windows()
    barplot(naux2,xlab=eval(expression(substitute(n[i],list(i=i)))),
   
arg.names=tit4,col="gray",width=c(anch,anch),axes=TRUE,xlim=c(0,anch*(esp+2)*length(nind)),
    space=esp,ylim=c(0,max(naux2)),main=paste("State
#",i),yaxp=c(0,M,Mint));lines(c(0,100),c(0,0))
    }   # end of for
 
but I don't get what I expect. R plots literally the contents of tit4 below
each bar, i.e., (for the last value of i in the outer for loop)

"expression(n[paste[5,1])" 
"expression(n[paste[5,2])" 
"expression(n[paste[5,3])" 
"expression(n[paste[5,4])"

Of course, if I write directly
arg.names=c(expression(n[paste(5,1)]),expression(n[paste(5,2)]),expression(n[paste(5,3)]),expression(n[paste(5,4)]))
it works, but then I cannot do ii in an automatic way for all the graphics
coming from the for (i in 1:dim(Ntot)[1]).

I have also tried to store in another variable tit5 the whole expression as
> tit5
[1]
"c(expression(n[paste[5,1]),expression(n[paste[5,2]),expression(n[paste[5,3]),expression(n[paste[5,4]))"
but it doesn't work neither

I wonder if there is some way that barplot "tells" arg.names to "evaluate"
the contents of tit4 as expressions, not as characters

I hope I made myself clear enough

Thanks in advance to any response

Cheers!!!!

Javi
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