[R] Substituting Greek symbols in some tick labels

[David Winsemius]

On Jul 4, 2013, at 8:14 PM, Eric Archer - NOAA Federal wrote:

> 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
> 8901 La Jolla Shores Drive
> La Jolla, CA 92037 USA
> 858-546-7121 (work)
> 858-546-7003 (FAX)
> 
> Marine Mammal Genetics Group: swfsc.noaa.gov/prd-mmgenetics
> ETP Cetacean Assessment Program: swfsc.noaa.gov/prd-etp
> 
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David Winsemius
Alameda, CA, USA