Get the index of the first/last TRUE

A quick C implementation for “which.first” (head(which(x), 1)) and “which.last” (tail(which(x), 1)).

wf(x, use.names = TRUE)

wl(x, use.names = TRUE)

Arguments

x

[logical]
Logical vector.

use.names

[logical(1)]
If TRUE and x is named, the result is also named.

Value

[integer(1) | integer(0)]. Returns the index of the first/last TRUE value in x or an empty integer vector if none is found. NAs are ignored.

Examples

wf(c(FALSE, TRUE))
#> [1] 2
wl(c(FALSE, FALSE))
#> integer(0)
wf(NA)
#> integer(0)