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Convert Vectors to Range String

to_range.Rd

Converts vectors to a string of ranges. All vector types are accepted and the original values will appear in the final output range, but where input is not a numeric vector of whole numbers, a function to convert the values to integers must be provided (int_fn) for the purpose of identifying the range(s).

Usage

to_range(
  x,
  int_fn = NULL,
  ...,
  sep = c(",", "-"),
  start_rm = NULL,
  end_rm = NULL
)

Arguments

x

A numeric vector of whole numbers.

int_fn

A function (or tidyverse-style formula) to convert x into an integer vector, used ONLY for creating ranges; the original value will appear in the range except where modified by start_rm and/or end_rm. int_fun is required when x is not a numeric vector.

...

Arguments passed on to int_fn.

sep

The separators to use between ranges (default: ',') and within a range (default: '-'), as a length-2 character vector.

start_rm

A regular expression to remove from x values at the beginning of a range.

end_rm

A regular expression to remove from x values at the end of a range.

Value

The range(s) formatted as a string or NA if the input is an empty vector.

Notes

  • NA values are always dropped.

  • to_range() was inspired by answers at https://stackoverflow.com/q/16911773/6938922, most heavily by speendo (CC-BY-SA 3.0, accessed 2022-07-01). This is the fastest approach with few inputs but is significantly slower than other answers for large inputs. The internal approach will likely be modified in the future, but arguments and output will remain the same.

Examples

x <- c(1:2, 8:6, 4, -1:-2, 20:37, 4, 40, 43, 45)
to_range(x)
#> [1] "-2,-1,1,2,4,6-8,20-37,40,43,45"


# `NA` values are dropped
y <- c(1:4, NA, 5, 7:10)
to_range(x)
#> [1] "-2,-1,1,2,4,6-8,20-37,40,43,45"


# Use `int_fn` when `x` is not a numeric vector (tidyverse-style formulas
#    accepted)
x_char <- as.character(x)
to_range(x, int_fn = as.integer)
#> [1] "-2,-1,1,2,4,6-8,20-37,40,43,45"
to_range(x, int_fn = ~ as.integer(.x))
#> [1] "-2,-1,1,2,4,6-8,20-37,40,43,45"


# `int_fn` allows non-numeric ranges to be created
txt <- paste0(x, "txt")
to_int <- function(x, y) as.integer(stringr::str_remove(x, "txt"))
to_range(txt, to_int, y = "txt")
#> [1] "-2txt,-1txt,1txt,2txt,4txt,6txt-8txt,20txt-37txt,40txt,43txt,45txt"


# text can be selectively removed from the values at the beginning of ranges
#     (`start_rm`) or end of ranges (`end_rm`)
to_range(txt, to_int, start_rm = "txt")
#> [1] "-2txt,-1txt,1txt,2txt,4txt,6-8txt,20-37txt,40txt,43txt,45txt"
to_range(txt, to_int, end_rm = "txt")
#> [1] "-2txt,-1txt,1txt,2txt,4txt,6txt-8,20txt-37,40txt,43txt,45txt"