Substituting Greek symbols in some tick labels

I have a character vector that I'm using to label ticks in a dotchart. Some
of the elements in the vector have an asterisk (*) where a Greek Delta
needs to be placed when the plot is generated. Here's a simple example:

x <- 1:4
x.lab <- c("a*a", "bbb", "c*c", "ddd")
dotchart(x, labels = x.lab)

The first and third labels should be 'a<Delta>a' and 'c<Delta>c'. I've
tried things like,

x.lab <- strsplit(x.lab, "[*]")
x.lab <- lapply(x.lab, function(y) expression(paste(y, sep = Delta)))

but because 'y' is unevaluated, the resulting list elements won't work as
tick labels. I've tried to modify it by using bquote and substitute, but
couldn't get anything closer. Any suggestions? Thanks!
Right. I would not throw away the "*" but rather change it to an inline Delta:

x.lab <- gsub("\\*", "*Delta*", x.lab)

# parse(text=x.lab)
# returns: expression(a*Delta*a, bbb, c*Delta*c, ddd)# 

Then parse it:

dotchart(x, labels = parse(text=x.lab) )
Cheers,
eric

-- 

Eric Archer, Ph.D.
Southwest Fisheries Science Center
NMFS, NOAA
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Substituting Greek symbols in some tick labels

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