Create custom annotate function

Question

I am struggling to modify ggplot2 annotate(). All I want to do, is create a slightly modified annotate() function (say, annotate_new()) which automatically places annotations in the top left corner with a certain text size.

Below, please find my try which somehow doesn't work:

annotate_new <- 
  function (geom, xmin = NULL, xmax = NULL, 
            ymin = NULL, ymax = NULL, xend = NULL, yend = NULL, 
            x=NULL, y=NULL, parse=TRUE, size = 12, ..., 
            na.rm = FALSE) {
    position <- compact(list(xmin = xmin, xmax = xmax, 
                             xend = xend, ymin = ymin, ymax = ymax, yend = yend,
                             x = -Inf, y = Inf, 
                             hjust = 0, vjust = 1))
    aesthetics <- c(position, list(...))
    lengths <- vapply(aesthetics, length, integer(1))
    n <- unique(lengths)
    if (length(n) > 1L) {
      n <- setdiff(n, 1L)
    }
    if (length(n) > 1L) {
      bad <- lengths != 1L
      details <- paste(names(aesthetics)[bad], " (", 
                       lengths[bad], ")", sep = "", collapse = ", ")
      stop("Unequal parameter lengths: ", details, call. = FALSE)
    }
    data <- vctrs::new_data_frame(position, n = n)
    layer(geom = "text", 
          params = list(na.rm = na.rm, ...), stat = StatIdentity, 
          position = PositionIdentity, data = data, mapping = aes_all(names(data)), 
          inherit.aes = FALSE, show.legend = FALSE)
  }


ggplot(mpg, aes(displ, hwy)) + 
  geom_point() + 
  annotate_new(label = corr_eqn(mpg$hwy, mpg$displ))

This creates:

Somehow, the text size isn't adjustable... Would really appreciate your help!

Answer 1

Instead of re-writing the source code would you be open to creating a wrapper for the annotate function?

annotate_new <- function(...){
  annotate('text',
           x = -Inf,
           y = Inf,
           size = 12, 
           hjust = 0,
           vjust = 1,
           ...)
}

ggplot(mpg, aes(displ, hwy)) + 
  geom_point()+
  annotate_new(label="Label")

This is the same function with some of your preferred defaults set and you can still pass through additional arguments via the '...' like the 'label'.

Answer 2

In your code, call size in the list of parmeters

annotate_new <- 
  function (geom, xmin = NULL, xmax = NULL, 
            ymin = NULL, ymax = NULL, xend = NULL, yend = NULL, 
            x=NULL, y=NULL, parse=TRUE, size = 12, ..., 
            na.rm = FALSE) {
    position <- compact(list(xmin = xmin, xmax = xmax, 
                             xend = xend, ymin = ymin, ymax = ymax, yend = yend,
                             x = -Inf, y = Inf, 
                             hjust = 0, vjust = 1))
    aesthetics <- c(position, list(...))
    lengths <- vapply(aesthetics, length, integer(1))
    n <- unique(lengths)
    if (length(n) > 1L) {
      n <- setdiff(n, 1L)
    }
    if (length(n) > 1L) {
      bad <- lengths != 1L
      details <- paste(names(aesthetics)[bad], " (", 
                       lengths[bad], ")", sep = "", collapse = ", ")
      stop("Unequal parameter lengths: ", details, call. = FALSE)
    }
    data <- vctrs::new_data_frame(position, n = n)
    layer(geom = "text", 
          params = list(na.rm = na.rm, size = size, ...), stat = StatIdentity, 
          position = PositionIdentity, data = data, mapping = aes_all(names(data)), 
          inherit.aes = FALSE, show.legend = FALSE)
  }


ggplot(mpg, aes(displ, hwy)) + 
  geom_point() + 
  annotate_new(label = "temp", size = 13)