Find the Closest Value

Find the value(s) in a vector closest to a reference value. Multiple values are returned if ties occur or if duplicate values share the same minimum distance.

Usage

closest(x, a, output = "value", na.rm = FALSE)

Arguments

x

a numeric vector to search in.

a

the reference value. May be a vector; see Details.

output

character string specifying the output representation. One of "value" (return the closest value(s), the default) or "index" (return the index position(s) in x). May be a vector; recycled to the length of a.

na.rm

logical. If TRUE, NA values in x are ignored before searching. Default is FALSE.

Value

if a and output are scalar:

• numeric vector if output = "value".

• integer vector if output = "index".

If a or output are vectors: a list with one element per value of a.

Returns NA if x is empty or all-NA (with na.rm = TRUE).

Details

Distance is computed as \(|x_i - a|\). Ties are detected via isZero() rather than exact equality, which avoids spurious misses due to floating-point representation (e.g. 0.3 - 0.2 != 0.1).

When na.rm = TRUE, NA elements are excluded from the search but the original index positions of the remaining elements are preserved, so output = "index" always refers to positions in the original x.

When a or output are vectors, each element is processed independently and a list is returned.

Recycling follows standard R rules.

See also

which()

Other math.basic: crossProd(), crossProdN(), dotProd(), roundTo(), unirootAll()

Examples

# basic
set.seed(8)
x <- runif(10) * 10

closest(x, 3.1)
#> [1] 3.215092

sort(x)
#>  [1] 2.078233 2.908734 3.215092 4.662952 6.444911 6.518713 7.189275 7.691470
#>  [9] 7.996580 9.322698

y <- sample(10, size = 10, replace = TRUE)

# multiple observations of the same closest value
closest(y, a = 6)
#> [1] 6 6

# get the relevant positions
closest(y, a = 6, output = "index")
#> [1] 5 6

# two different values having the same distance (tie)
closest(c(2, 3, 4, 5), a = 3.5)
#> [1] 3 4

# na.rm preserves original index positions
closest(
  c(NA, 5, 8),
  a = 6,
  output = "index",
  na.rm = TRUE
)  # 2, not 1
#> [1] 2

# vectorize "a"
closest(c(2, 3, 4, 5), a = c(3.1, 3.9))
#> [[1]]
#> [1] 3
#> 
#> [[2]]
#> [1] 4
#> 

# vectorize "output"
closest(
  c(2, 3, 4, 5),
  a = 3.1,
  output = c("value", "index")
)
#> [[1]]
#> [1] 3
#> 
#> [[2]]
#> [1] 2
#> 

closest(
  c(2, 3, 4, 5),
  a = c(3.1, 3.9),
  output = c("value", "index")
)
#> [[1]]
#> [1] 3
#> 
#> [[2]]
#> [1] 3
#>