How does one pass additional parameters to a ggplot generated inside a function?

Question

I write many packages where the generic plot is a ggplot2. A ggplot call, unlike other R function calls, is layered so one could end up with several options (separated by + signs) to get a plot looking just right. However, I don't want someone to suffer through my pre-defined options and would like them to be able to customize it without re-writing my function from scratch. How do I accomplish this?

With a traditional function, I could use the three dot operator to pass optional arguments. This seems harder with a ggplot.

Reproducible example

f <- function(df) {
 custom_plot <-  ggplot(df, aes(mpg, disp, color = gear)) + 
geom_point(size = 3) +  
theme(panel.background = element_blank(), panel.grid.major = element_blank(),
        panel.grid.minor = element_blank(), panel.border = element_blank(),
        axis.line = element_line(colour = "black"))
        return(custom_plot)
}

To generate a plot

f(mtcars)

produces this:

A test plot

How do I generalize this function such that someone could pass additional or different options to this plot (especially in cases where it is the generic plot)?

If my function were defined as:

f <- function(df, ...)

How would I pass those in to my ggplot call?

I gave up writing functions in this style (arguments defining plot options) a while ago, in favor of returning a basic ggplot object that can then be customized via + as needed outside the function. — joran
– joran, Commented Dec 12, 2012 at 2:53
Thanks @joran That's good to know. This was a request from a user and I totally forgot that the resulting object can still be modified outside the function call. — Maiasaura
– Maiasaura, Commented Dec 12, 2012 at 6:36

Marius · Accepted Answer · 2012-12-12 03:09:20Z

6

The plots returned by your functions should be modifiable for anyone who knows ggplot- unless you can think of specific cases that can't be fixed by using +, a better solution might be to do as little theming and customization as possible, and let people add to the plots themselves.

All of these customizations work fine, for example:

mtplot <- f(mtcars)
mtplot + theme_bw()
mtplot + scale_colour_gradientn(colours=c("red", "purple"))
mtplot + labs(title="Add a title!")
mtplot + geom_point(size=5)

answered Dec 12, 2012 at 3:09

Marius

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Comments

qfazille · Accepted Answer · 2023-10-26 12:30:03Z

0

tt <- function(x, ...) {
  ap <- list(...)
  ggplot(x, aes(x = Sepal.Length, y = Petal.Length, colour= Species)) +
    geom_point() +
    ap
}

tt(x = iris)
tt(x = iris, scale_colour_manual(values = c("#da291c", "#64009b", "#127ae3")))
tt(x = iris, scale_colour_manual(values = c("#da291c", "#64009b", "#127ae3")), labs(title = "Example with iris"))

answered Oct 26, 2023 at 12:30

qfazille

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