Determines the location (i.e., index) of the (first, last, or all) minima or maxima of a numeric (or logical) vector.
Arguments
- x
numeric (logical, integer or double) vector or an R object for which the internal coercion to double works whose min or max is searched for.
- loc
'first','last'or'all'to specify which index/indices to return.- value
value/s to replace the min or max values with when using the assignment functions.
Value
integer of indices. For the assignment functions, the
modified object with min or max values replaced by value.
Note
For logical vectors, which(x) is faster than
whichMax(x, loc = "all"), but whichMin(x, loc = "all") can
be faster than which(!x) for medium to large vectors due to
not having the performance cost of negating the vector.
Examples
x <- c(1:4, 0:5, 11, 1:4, 0:5, 11)
whichMin(x)
#> [1] 5
whichMin(x, loc = "last")
#> [1] 16
whichMax(x)
#> [1] 11
whichMax(x, loc = "all")
#> [1] 11 22
# it *does* work with NA's present, by discarding them:
presidents[1:30]
#> [1] NA 87 82 75 63 50 43 32 35 60 54 55 36 39 NA NA 69 57 57 51 45 37 46 39 36
#> [26] 24 32 23 25 32
whichMin(presidents) # 28
#> [1] 28
whichMax(presidents) # 2
#> [1] 2
# Find the first occurrence, i.e. the first TRUE, if there is at least one:
x <- rpois(10000, lambda = 10)
x[sample.int(50, 20)] <- NA
# where is the first value >= 20 ?
whichMax(x >= 20)
#> [1] 911
whichMax(x >= 20, loc = "last")
#> [1] 9393
whichMax(x >= 20, loc = "all")
#> [1] 911 2414 2895 3322 3511 3709 3953 4124 4268 4590 4592 4947 5180 5231 5681
#> [16] 5803 5989 5991 6171 6494 7028 7107 7189 7295 7456 7789 7905 7936 7989 8029
#> [31] 8274 8516 8530 8667 8747 8758 9393
# objects are coerced to numeric vectors if possible:
whichMin(list(A = 7, pi = pi)) ## -> c(pi = 2L)
#> pi
#> 2
x <- 1:4
whichMin(x) <- 999
whichMax(x) <- -999
x
#> [1] -999 2 3 4