R ggplot2 doesn't know a custom function

Question

I'm not happy with scales::percent, for example, scales::percent(21/80) returns "26.2%" while I'd prefer getting "26.25%". So I wrote a quick function:

custom_percent <- function(x, digits = 2) {
  paste0(round(100 * x, digits = digits), "%")
}

However, when I try to use it with ggplot2, I receive the following error "Error in eval(expr, envir, enclos) : could not find function "custom_percent". Here is an example:

dset <- data.frame(data = 10:90)
p <- ggplot(dset, aes(x = data))
p + geom_bar(aes(y = (..count..)/sum(..count..)), width = .5) +
  geom_text(aes(y = ((..count..)/sum(..count..)),
            label = custom_percent((..count..)/sum(..count..))),
            stat = "count", vjust = -0.25) +
  scale_y_continuous(labels = custom_percent)

What can I do to access custom_percent?

I'm not sure if it's a problem with ggplot not being able to find the custom function. For example, d <- data.frame(x=1:10, y=rnorm(10)) and then ggplot(d) + geom_text(aes(x, y, label = custom_percent(y))) works perfectly fine. — Weihuang Wong
– Weihuang Wong, Commented Oct 23, 2016 at 0:23
It seems like a problem that's specific to using the special variables (like ..count..) together with a custom function. Interesting. — Weihuang Wong
– Weihuang Wong, Commented Oct 23, 2016 at 0:34
It was unexpected as when I used scales::percent everywhere instead, it just worked. But then scales was by the same author who wrote ggplot2 so maybe he used a trick in both. — green diod
– green diod, Commented Oct 23, 2016 at 7:07
it sounded like setting an environment should have helped, but it doesn't appear to work — baptiste
– baptiste, Commented Oct 23, 2016 at 19:58
Hi @baptiste, actually, given all the questions about capturing arguments or local variables in aes, that was the first path I tried. And of course it miserably failed. Maybe because, in my case, the ggplot and aes calls were not inside a function definition. — green diod
– green diod, Commented Oct 24, 2016 at 7:06

Community · Accepted Answer · 2017-05-23 12:06:46Z

2

aes_q and bquote can help with these tricky scoping issues,

dset <- data.frame(data = 10:90)
p <- ggplot(dset, aes(x = data))
p + geom_bar(aes_(y = ~(..count..)/sum(..count..)), width = .5) +
  geom_text(aes_(y = ~((..count..)/sum(..count..)),
                label = bquote(.(custom_percent)((..count..)/sum(..count..)))),
            stat = "count", vjust = -0.25) +
  scale_y_continuous(labels = custom_percent)

edited May 23, 2017 at 12:06

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answered Oct 23, 2016 at 19:58

baptiste

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5 Comments

Brandon Bertelsen Over a year ago

I think aes_string() would solve this in a similar way too. With the whole expression in quotes.

baptiste Over a year ago

@BrandonBertelsen what is this, Matlab? ;)

Brandon Bertelsen Over a year ago

Ugly, but functional, just_like_matlab.

green diod Over a year ago

@baptiste So is it aes_ or aes_q? What's the difference? Was this family of functions (and bquote as well) recently introduced?

green diod Over a year ago

@baptiste I accepted your answer but truly, there should be a better way to do it. Anyway, a plain aes call seems to stumble upon using the special stats ..some_stat... By the way, do you know where all these special stats are listed?

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