number(accuracy = NULL) heuristic can fail

[davidchall]

The label_number family of functions have a default value of accuracy = NULL. According to the documentation, this:

uses a heuristic that should ensure breaks have the minimum number of digits needed to show the difference between adjacent values.

Unfortunately, it seems this heuristic can fail under certain conditions. Here's an example:

> scales::comma(c(Inf, 1, Inf, 0))
Error in if (smallest_diff < sqrt(.Machine$double.eps)) { : 
  missing value where TRUE/FALSE needed

It looks like the problem stems from the underlying scales::number function:

> scales::number(c(Inf, 1, Inf, 0))
Error in if (smallest_diff < sqrt(.Machine$double.eps)) { : 
  missing value where TRUE/FALSE needed

[teunbrand]

I think part of the problem might be duplicate values, which is not checked for in the scales:::precision() internal function.

library(scales)
#> Warning: package 'scales' was built under R version 3.6.2
number(c(1, 2, 3))
#> [1] "1.0" "2.0" "3.0"
number(c(1, 2, 2, 3))
#> [1] "1" "2" "2" "3"

^{Created on 2020-02-16 by the reprex package (v0.3.0)}

It seems like deduplicating the x * scale input before passing it to the scales:::precision function alleviates some errors:

library(scales)
#> Warning: package 'scales' was built under R version 3.6.2
library(rlang) # for the %||% operator


number2 <- function (x, accuracy = NULL, scale = 1, prefix = "", suffix = "", 
                     big.mark = " ", decimal.mark = ".", trim = TRUE, 
                     ...) 
{
  if (length(x) == 0) 
    return(character())
  # Deduplicate x before passing to precision
  accuracy <- accuracy %||% scales:::precision((x * scale)[!duplicated(x)])
  x <- scales:::round_any(x, accuracy/scale)
  nsmall <- -floor(log10(accuracy))
  nsmall <- min(max(nsmall, 0), 20)
  ret <- format(scale * x, big.mark = big.mark, decimal.mark = decimal.mark, 
                trim = trim, nsmall = nsmall, scientific = FALSE, ...)
  ret <- paste0(prefix, ret, suffix)
  ret[is.infinite(x)] <- as.character(x[is.infinite(x)])
  ret[is.na(x)] <- NA
  names(ret) <- names(x)
  ret
}

# Some examples
ex1 <- c(1, 2, 3)
ex2 <- c(1, 2, 2, 3)
ex3 <- c(Inf, 1, Inf, 0)

number2(ex1)
#> [1] "1.0" "2.0" "3.0"
number2(ex2)
#> [1] "1.0" "2.0" "2.0" "3.0"
number2(ex3)
#> [1] "Inf" "1.0" "Inf" "0.0"

^{Created on 2020-02-16 by the reprex package (v0.3.0)}

But I don't know whether you would want the -.0 if the input are rounded numbers, but that might a different issue altogether.