R help - Aug 2013 - alignment problem for italicised legend text in pdf output from a barplot

A minimal R source code file producing this is:

data=c(1,2)
pdf(file="error.pdf")
barplot(data)
legend(1.5,c(expression(italic("C.sativa"),italic("B.rapa"))),horiz=TRUE)
dev.off()

The problem is that the two italicised strings are not aligned in the pdf
output, with the string on the left being lower than the string on the right by
size of about two dots. Removing the calls to expression and italic produces
correct alignment, but italic is required in the final figure.

The R version information etc. follows.
> version
               _
platform       i386-pc-mingw32
arch           i386
os             mingw32
system         i386, mingw32
status
major          2
minor          14.1
year           2011
month          12
day            22
svn rev        57956
language       R
version.string R version 2.14.1 (2011-12-22)


Dr. John Nixon
Research Scientist/Chercheur Scientifique
Agriculture and Agri-Food Canada / Agriculture et Agroalimentaire Canada
Office Address / Adresse du bureau:
107 Science Place, Saskatoon SK S7N 0X2
E-mail Address / Adresse courriel: 
John.Nixon@agr.gc.ca<mailto:John.Nixon@agr.gc.ca>
Telephone /Téléphone 306-956-2844
Facsimile / Télécopieur 306-956-7247
Teletypewriter / Téléimprimeur 613-773-2600
Government of Canada / Gouvernement du Canada




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On Aug 20, 2013, at 2:28 PM, Nixon, John wrote:
> A minimal R source code file producing this is:
> 
> data=c(1,2)
> pdf(file="error.pdf")
> barplot(data)
>
legend(1.5,c(expression(italic("C.sativa"),italic("B.rapa"))),horiz=TRUE)
> dev.off()
> 
> The problem is that the two italicised strings are not aligned in the pdf
output, with the string on the left being lower than the string on the right by
size of about two dots. Removing the calls to expression and italic produces
correct alignment, but italic is required in the final figure.
> 
It's being caused by the descender of the letter "p". There are no
letters with descenders in the first expression. `phantom` lets you add space
and apparently does so both horizonatly which I how I've used it before and
vertically as this demonstrates.  Do this:

data=c(1,2)
pdf(file="error.pdf")
barplot(data)
legend(1.5,c(expression( phantom("p")*italic("C.sativa"),
italic("B.rapa"))),horiz=TRUE)
dev.off()

-- 

David Winsemius
Alameda, CA, USA