Transferring commas in character vector to expression

Duncan,

Thanks for the suggestion, but that won't work for my situation. I'm trying
to use a character vector to label some axis ticks. There are some elements
in the vector that have either a comma, or both Greek symbols and a comma,
like the the third and fourth elements in x.lab below:

x <- 1:4
x.lab <- c("a*a", "bbb", "c,cc*c", "d,dd")
x.lab <- gsub("\\*", "*Delta*", x.lab)
x.lab <- parse(text = x.lab)

Error in parse(text = x.lab) : <text>:3:2: unexpected ','
2: bbb
3: c,
   ^

dotchart(x, labels = x.lab)

The root problem that I'm stumped on is how to either:
1) insert a comma into an expression and have it be read as a valid
character, or
2) replace the comma in the character string with 'list(a, b, c)' as in the
help for plotmath and have it interpreted correctly.

Cheers,
eric


On Sat, Jul 6, 2013 at 3:33 PM, Duncan Mackay <mackay at northnet.com.au>wrote:

Hi Eric

I have not been following the thread but following on what David has said
on previous occasions

try for example

plot(1,1, ylab =  expression("aa aaa,aa bb"*Delta*"b cccc"*Delta*"cc, c") )

Below is from a partly saved previous post of David's several months ago
which may give you some ideas

DATA_names<-c(
"A mg kg",
"B mg kg",
"C mg kg",
"D mg kg",
"E mg kg",
"F mg kg",
"G mg kg",
"H mg kg")

pos <- barplot(1:length(DATA_names))
text(x=pos,y=-1, xpd=TRUE, srt=45,
                   labels= sapply( gsub("mg kg", "(mg kg)^-1", DATA_names),
                                   as.expression))

HTH

Duncan


Duncan Mackay
Department of Agronomy and Soil Science
University of New England
Armidale NSW 2351
Email: home: mackay at northnet.com.au




At 07:47 6/07/2013, you wrote:

I'm trying to format a given character vector as an expression with Greek
symbols to be used in labeling axis ticks. Thanks to some help from David
Winsemius, I've learned how to make the substitution and place the Greek
symbols in, however I've run into another problem: Some of my labels have
commas in them, so when the parse command is executed, there is an
unexpected symbol error. For example:

x <- c("aa", "aaa,aa", "bb*Delta*b", "cccc*Delta*cc,c")
parse(text = x)

Error in parse(text = x) : <text>:2:4: unexpected ','
1: aa
2: aaa,
     ^

I've tried various iterations of wrapping the commas in interior quotes
("aaa\",\"aa"), but then the error shifts to the quote. I see in plotmath
that 'list(a,b,c)' gives me comma separated values, but I haven't been
able
to work out how to get this construction for elements that have a comma.

Is this possible?

--

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

"The universe doesn't care what you believe.
 The wonderful thing about science is that it
   doesn't ask for your faith, it just asks
   for your eyes."  - Randall Munroe

"Lighthouses are more helpful than churches."
   - Benjamin Franklin

   "...but I'll take a GPS over either one."
       - John C. "Craig" George

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--

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

"The universe doesn't care what you believe.
 The wonderful thing about science is that it
   doesn't ask for your faith, it just asks
   for your eyes."  - Randall Munroe

"Lighthouses are more helpful than churches."
   - Benjamin Franklin

   "...but I'll take a GPS over either one."
       - John C. "Craig" George

        [[alternative HTML version deleted]]