formatting ggplot scales with s3 method and objects attributes - r

Question

I have two custom classes that have different types of constructors and different types of formatting methods, one class relying on the attributes of the object.
as.test_1 <- function(x, test_attribute, ...) {
attributes(x) <- list("test_attribute" = test_attribute)
x <-
structure(x, class = c("test_1", setdiff(class(x), "test_1")))
return(x)
}
format.test_1 <- function(x, ...) {
paste0(x, attributes(x)$test_attribute)
}
print.test_1 <- function(x, ...) {
cat(format(x, ...), "\n")
}
as.test_2 <- function(x, test_attribute, ...) {
x <-
structure(x, class = c("test_2", setdiff(class(x), "test_2")))
return(x)
}
format.test_2 <- function(x, ...) {
paste0(x, "test")
}
print.test_2 <- function(x, ...) {
cat(format(x, ...), "\n")
}
Now I want to to plot some data that contains these classes:
library(data.table)
data_1 <-
data.table(a = as.test_1(c(1, 2, 3, 4), test_attribute = "test"),
b = as.factor(c("a", "b", "c", "d")))
data_2 <-
data.table(a = as.test_2(c(1, 2, 3, 4), test_attribute = "test"),
b = as.factor(c("a", "b", "c", "d")))
Also I want to use the format method to format the y-axis. This is my first try, which works for the test_2 class that does not rely on the attributes of the variable for formatting:
library(ggplot2)
plot_data <- function(data) {
g <- ggplot(data, aes(x = b, y = a))
g <- g + geom_bar(stat = "identity")
expand <- c(0, 0)
attributes(expand) <- attributes(data$a)
limits <- c(0, 4)
attributes(limits) <- attributes(data$a)
g <- g + scale_y_continuous(
expand = expand,
limits = limits,
oob = scales::squish,
labels = getS3method(f = "format", class = class(data$a)[[1]])
)
return(print(g))
}
However for the test_1 class it seems like the attributes get lost somewhere in the call of scale_y_continuous.
plot_data(data_1)
plot_data(data_2)
Does someone know how to fix this?
Thanks!