Merging expressions for plotting

Question

I'm trying to merge two expressions made with bquote. For example:

a = 1
b = 2

x1 = as.expression(bquote(paste("Something ", alpha, " = ", .(a), sep = "")))
x2 = as.expression(bquote(paste("Something else ", beta, " = ", .(b), sep = "")))

Is there a way to do something similar to x12 = paste(x1, x2, collapse = "some symbol") without doing:

x12 = as.expression(bquote(paste("Something ", alpha, " = ", .(a)," some symbol ",
"Something else ", beta, " = ", .(b), sep = "")))

Thanks a lot!

Answer 1

You can write a small function that combines plotmath expressions:

a = 1
b = 2

x1 = bquote("Something " * alpha == .(a))
x2 = bquote("Something else " * beta == .(b))

comb_plotmath <- function(...) {
  Reduce(function(x, y) substitute(x * y, env = list(x = x, y = y)), 
         list(...))
}


plot.new()
text(0.5, 0.5, comb_plotmath(x1, " some symbol ", x2))

Results in:

Note that paste in plotmath has no sep parameter. You might want to study help("plotmath").