Feature request: hold argument for label_* functions

[davidhodge931]

I would like to have flexibility in labelling functions to keep only a subset of the labels.

Some use cases include:

• colourbars where you only want a range on the guide
• coloursteps where you want lots of steps, but you don't want a label for each
  etc

In particular, I want to:

• label only the min/max break
• label only every second break starting at 1
• label only every second break starting at 2
  etc

So the other non-kept breaks would need to be returned as "".

An idea to implement this would be as a hold argument in label_* functions that could accept a function.

label_*(hold = \(x) range(x))(1:7) #keep labels in a range
c("1", "", "", "", "", "", "7")

label_*(hold = \(x) x[seq(1, length(x), by = 2))(1:7) #keep every 2nd label starting from the 1st
c("1", "", "3", "", "5", "", "")

label_*(hold = \(x) x[seq(1, length(x), by = 2))(1:7) #keep every 2nd label starting from the 2st
c("1", "", "3", "", "5", "", "7")

label_*(hold = \(x) x[seq(2, length(x), by = 2))(1:7) #keep every 2nd label starting from the 2nd
c("", "2", "", "4", "", "6", "")

label_*(hold = \(x) x[seq(1, length(x), by = 3))(1:7)
c("1", "", "", "4", "", "", "7")

[davidhodge931]

Just noticed {purrr} has a function to keep elements, where it is using the word as a synonym for filter.

So prob a different word like hold is better then. Also is kind of like in poker, where the non-held elements could be considered folded as "".

I've created 2 functions that could be used with a hold argument:

• hold_nth(x, nth = 2, offset = NULL)
• hold_range(x))

Not sure how you feel about this hold idea? If you like it, and want to implement it, you could also release hold_nth and hold_range functions in {scales}? Otherwise, I'll release my (hacky) functions in {ggblanket} shortly

https://github.com/davidhodge931/ggblanket/blob/main/R/hold.R