apply a function against a dimension
Similar to other apply functions, this takes an array and applies the
function against the dimensions (specified in the MARGIN argument). These
dimensions must be a single number (unlike many apply functions). See the
examples below, where we use the function add_one_hundred to add 100 on
to the end of each MARGIN.
applyAgainst(X, MARGIN, FUN, ...)
X |
an array |
MARGIN |
the dimension to apply the function against |
FUN |
the function to be applied |
... |
optional arguments to 'FUN“ |
FUN can be any function that takes a vector and returns a vector, but one
common use case is a function that adds new entries to the vector,
effectively expanding the array in the dimension given.
an array with the function applied
array <- array(c(1:24), dim = c(4, 3, 2)) array # , , 1 # # [,1] [,2] [,3] # [1,] 1 5 9 # [2,] 2 6 10 # [3,] 3 7 11 # [4,] 4 8 12 # # , , 2 # # [,1] [,2] [,3] # [1,] 13 17 21 # [2,] 14 18 22 # [3,] 15 19 23 # [4,] 16 20 24 add_one_hundred <- function(x) c(x, 100) crunch:::applyAgainst(array, 1, add_one_hundred) # , , 1 # # [,1] [,2] [,3] # [1,] 1 5 9 # [2,] 2 6 10 # [3,] 3 7 11 # [4,] 4 8 12 # [5,] 100 100 100 # # , , 2 # # [,1] [,2] [,3] # [1,] 13 17 21 # [2,] 14 18 22 # [3,] 15 19 23 # [4,] 16 20 24 # [5,] 100 100 100 crunch:::applyAgainst(array, 2, add_one_hundred) # , , 1 # # [,1] [,2] [,3] [,4] # [1,] 1 5 9 100 # [2,] 2 6 10 100 # [3,] 3 7 11 100 # [4,] 4 8 12 100 # # , , 2 # # [,1] [,2] [,3] [,4] # [1,] 13 17 21 100 # [2,] 14 18 22 100 # [3,] 15 19 23 100 # [4,] 16 20 24 100 crunch:::applyAgainst(array, 3, add_one_hundred) # , , 1 # # [,1] [,2] [,3] # [1,] 1 5 9 # [2,] 2 6 10 # [3,] 3 7 11 # [4,] 4 8 12 # # , , 2 # # [,1] [,2] [,3] # [1,] 13 17 21 # [2,] 14 18 22 # [3,] 15 19 23 # [4,] 16 20 24 # # , , 3 # # [,1] [,2] [,3] # [1,] 100 100 100 # [2,] 100 100 100 # [3,] 100 100 100 # [4,] 100 100 100
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