[R] label chemical formulas

Roberto Canteri canteri at itc.it
Mon Aug 4 16:44:58 CEST 2003

Dear r-help,
the prcomp matrix (x$rotation) I have, has the columns labels as chemical
formulas (i.e: C2H3, 37Cl,...,C10H24N3O3).
Plotting them as plain text I do the following with success:

xlabs <- dimnames(y$rotation)[[1]]
 xlabs <- as.character(xlabs)
 plot(y$rotation[,1],y$rotation[,2], ann=FALSE, type="p", col="red", pch=20)
 text(y$rotation[,1],y$rotation[,2], labels=xlabs, cex=0.7, font=1, pos=4,

 I do not succed to plot the labels with subscripts and superscripts. I did many
attempt trying the use of expression() or substitute() but without success. I
write the labels in the data matrix as needed (i.e.: C[2]*H[3]) to plot properly
if I would know how.
I peg your pardon if this is probably a silly problem, I am new user of R (I am
using R 1.7.0 on win2k).
Many thanks in advance for any help.

Roberto Canteri

Research Scientist
Physics-Chemistry of Surfaces and Interfaces Division |
|Tel. (+39) 0461 314 486
Centre for the scientific and technological research      | Fax  (+39) 0461 810
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E-mail:canteri at itc.it
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