Return Unique Value for Invariant Vectors

Returns the unique value from an input, if and only if, only 1 unique value exists (i.e. the input is invariant), otherwise returns the original input. Uniqueness is determined by base::unique() for flexibility but unique_if_invariant() may fail for custom methods.

Usage

unique_if_invariant(x, na.rm = FALSE, incl_nm = FALSE, ...)

Arguments

x

An R object, except arrays which are not supported.

na.rm

A logical scalar indicating whether NA values should be removed (default: FALSE); powered by stats::na.omit() and may be limited by its methods.

incl_nm

A logic scalar indicating whether names should also be examined (default: FALSE).

...

Arguments passed on to base::unique() methods.

See also

For unconditional vector-to-string conversion methods, see the vctr_to_string() family of functions.

Examples

unique_if_invariant(c("a", "a"))
#> [1] "a"
unique_if_invariant(c("a", "b"))
#> [1] "a" "b"

# `NA` can be ignored
unique_if_invariant(c("a", NA))
#> [1] "a" NA 
unique_if_invariant(c("a", NA), na.rm = TRUE)
#> [1] "a"

# names are ignored by default (and often dropped); to consider and preserve
# them use `incl_nm = TRUE`
unique_if_invariant(c(a = "A", b = "A"))
#> [1] "A"
unique_if_invariant(c(a = "A", b = "A"), incl_nm = TRUE)
#>   a   b 
#> "A" "A" 
unique_if_invariant(c(a = "A", a = "A"), incl_nm = TRUE)
#>   a 
#> "A" 

# na.rm & incl_nm are ignored for matrices & data.frames due to undesirable
# results; as with base::unique(), matrix comparison preserves columns
m <- matrix(rep(1, 4), 2)
unique_if_invariant(m)
#>      [,1] [,2]
#> [1,]    1    1

.df <- data.frame(m, check.names = TRUE)
unique_if_invariant(.df)
#>   X1 X2
#> 1  1  1