how to use expression in in names.arg function

Question

I have several carbon compounds in my bar graph but I need to subscript the numbers associated with each one, e.g. C*12*-C*16*, C*17*-C*25*,C*26*-C*32*,C*33*-C*37*.

I am trying to use the expression function but it is not going well with the names.arg function on barplot. Please see the code so far:

barplot(t(as.matrix(alkane)),
  ylim=c(0,100),
  names.arg=c("C12-C16","C17-C25","C26-C32","C33-C37"),
  xlab="Hydrocarbons analysed after 21 days",
  ylab="% loss in concentration relative to day 0",
  cex.lab=0.8,
  cex.axis=0.8,
  cex.names=0.8,
  cex.main=0.8,
  beside=TRUE,
  col=c("blue","red"))

Any help would be really appreciated.

Answer 1

I suppose you are looking for this:

set.seed(1)
x <- matrix(rbeta(8, 5, 5), 2, 4)

barplot(x, names.arg = 
          expression(C[12]-C[16], C[17]-C[25], C[26]-C[32],C[33]-C[37]))

Answer 2

As you can see with the highlighting it is not properly formatted your names.arg, check the " to be paired:

names.arg=c("C12-C16","C17-C25","C26-C32","C33-C37"),