Add an argument to theme in ggplot2

Question

I have a global variable with the theme for ggplot2:

cPlotOpts <- opts (axis.text.x = theme_text (size=10, colour="grey50"), axis.text.y = theme_text (…

and I would like to add one argument to it later in the code but without modifying those already set, so that

axis.text.x = theme_text (size=10, colour="grey50", angle=90)

How can I add this one argument (angle) to the already defined theme_text without having to explicitly repeat the settings for size and colour?

[Edited after the first answer for greater clarity.]

Answer 1

I think the easiest approach is to just use a function.

cPlotOpts <- function(size = 10, colour = "grey50", ...) {
  opts(axis.text.x = theme_text (size=size, colour=colour, ...))
}

then to add an argument later, simply:

cPlotOpts(angle=90)

which yields:

cPlotOpts(angle=90)
$axis.text.x
theme_text(colour = colour, size = size, angle = 90)

attr(,"class")
[1] "options"

If you do not want it edited, just use cPlotOpts(). Is something like that acceptable?