rmacos-monterey

R/apple problem: error in table() : all arguments must have the same length


I am currently working on an R package, in which I want to build a list of frequency tables of each column of a matrix. When testing on a

macOS Monterey Version 12.6.3 (21G419)

using

R version 4.0.5 (2021-03-31) -- "Shake and Throw" Platform: x86_64-apple-darwin17.0 (64-bit)

the following problem occurs (here reduced to an MWE):

test = matrix(sample(1:5, 1000, TRUE), 100,10)
str(test)
# int [1:100, 1:10] 4 4 2 5 3 1 2 4 5 1 ...

apply(test, 2, table, simplify = FALSE)

Error in FUN(newX[, i], ...) :

   all arguments must have the same length

On a newer apple and on a windows machine, the code ran without a problem, hence it seems to be associated with the old version. My problem: I'd like to make the package also available to users of the older version rather than demanding an update.

Is anyone aware of a solution/workaround? The code seems correct and the matrix has no missings, factors, or other peculiarities. Why would such an error be thrown?


Solution

  • As Roland stated in the comments, apply() gained the simplify argument in R 4.1.0. The docs for earlier versions show:

    apply(X, MARGIN, FUN, …)
    

    The ... argument is defined as:

    optional arguments to FUN.

    This means that apply(test, 2, table, simplify = FALSE) is translated as:

    apply(test, 2, function(x) table(x, simplify = FALSE))
    

    As simplify is not a named argument to table(), it is absorbed into the ellipsis and assumed to be a named vector. You are therefore doing something like:

    table(1:10, 0)
    

    Hence the error message: all arguments must have the same length.

    To circumvent this, you can use asplit() on R 3.6.0 and greater to split the matrix into a list of columns, and then iterate over it:

    lapply(asplit(test, 2), table)
    

    On versions earlier than 3.6.0, e.g. 3.5.2 you can do:

    lapply(split(test, slice.index(test, 2)), table)