pasting together two vectors with expression command

Question

I'm trying to create a y-axis label that is generated by pasting together two vectors that are the same length. The catch is that the first element needs to be italicized. Here's an example...

n <- 1:5
t <- LETTERS[1:5]
together <- paste(t, n)

plot(x=1:5, y=1:5, yaxt="n")
axis(2, at=1:5, label=together, las=2)

So, I'd like the t elements italicized. I've looked around expression, bquote, and substitute and am not making much progress. Anyone got a hint to help me here?

Answer 1

This is a bit tricky because the expression function expects a list of expressions. Therefore you need to convert the strings returned by paste to a list of unevaluated expressions. One way is like this

together <- do.call(expression, as.list(parse(text = paste0("italic(", t, ")~", n))))

Answer 2

You could use bquote

together <- as.expression(sapply(seq_along(t), function(i) 
                   bquote(italic(.(t[i]))*.(n[i]))))

Or using for loop

 v1 <- c()
 for(i in seq_along(t)){
   v1 <- c(v1, bquote(italic(.(t[i]))*.(n[i])))
  }
 together <- as.expression(v1)