[R] using subscripts in a plot title with 2 lines

[Rajarshi Guha]

Hi,
  I'm making a plot in which the title takes up two lines. The title
contains a subscript but when I look at the plot it does'nt seem tocome
out properly. The code I'm using is:

   xtxt = expression(paste('Observed -log( ', IC[50], ' )'))
   ytxt = expression(paste('Predicted -log( ', IC[50], ' )'))
   mtxt = expression(paste('Plot of Observed vs. Predicted -log(',
IC[50], ') Values for the PDGFR\nDataset'))

   plot(tset$V2, tset$V3, xlim = c(-2,2), ylim = c(-2,2),
    pch = 19, col = "blue", 
    main=mtxt,
    xlab = xtxt,
    ylab = ytxt)

Removing the IC[50] term makes it come out OK. 
Is there any way to get around this?

Thanks,

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Rajarshi Guha <rxg218 at psu.edu> <http://jijo.cjb.net>
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