Modify an array by mapping over 1 or more dimensions

This function can be thought of as a version of base::apply() that is guaranteed to return a object of the same dimensions as it was input. It also generally preserves attributes, as it's built on top of [<-.

modify_along_dim(X, which_dim, .f, ...)

modify_along_rows(X, .f, ...)

modify_along_cols(X, .f, ...)

Arguments

X	An array, or a list of arrays
which_dim	integer vector of dimensions to modify at
.f	a function or formula defining a function(same semantics as purrr::map()). The function must return either an array the same shape as it was passed, a vector of the same length, or a scalar, although the type of the returned object does not need to be the same as was passed in.
...	passed on to .f()

Value

An array, or if X was a list, a list of arrays of the same shape as was passed in.

Examples

x <- array(1:6, 1:3)
modify_along_dim(x, 3, ~mean(.x))
#> , , 1
#> 
#>      [,1] [,2]
#> [1,]  1.5  1.5
#> 
#> , , 2
#> 
#>      [,1] [,2]
#> [1,]  3.5  3.5
#> 
#> , , 3
#> 
#>      [,1] [,2]
#> [1,]  5.5  5.5
#> 
modify_along_dim(x, 3, ~.x/mean(.x))
#> , , 1
#> 
#>           [,1]     [,2]
#> [1,] 0.6666667 1.333333
#> 
#> , , 2
#> 
#>           [,1]     [,2]
#> [1,] 0.8571429 1.142857
#> 
#> , , 3
#> 
#>           [,1]     [,2]
#> [1,] 0.9090909 1.090909
#>