Writing ggplot functions in R with optional arguments

Question

I have a series of ggplot graphs that I\'m repeating with a few small variations. I would like to wrap these qplots with their options into a function to avoid a lot of repetiti

Answer 1

Note that you can also use missing(facets) to check if the facets argument was specified or not. If you use @JD Long's solution, it would look something like this:

qhist <- function(variable, df, heading, facets) {
  ... insert @JD Longs' solution ...

  if (!missing(facets)) d <- d + facet_wrap(as.formula(paste("~", facets)))
  return(d)
}

...Note that I also changed the default argument from facets=NULL to just facets.

Many R functions use missing arguments like this, but in general I tend to prefer @JD Long's variant of using a default argument value (like NULL or NA) when possible. But sometimes there is no good default value...