R - Compare vector of objects using Reduce-CodePudding

I am trying to compare vector a of objects using Reduce

all.equal does not work
== works for numericals but will not be sufficient for objects.

I would prefer a solution that does not use existing packages but R core functions only

Example (Simplified to use numeric vectors instead of objects):

test <- c(1,1,1,1,1)

Reduce("==",test)

[1] TRUE

I do not understand why == works while all.equal does not

Reduce(all.equal,test)

[1] "Modes: character, numeric"              
[2] "Lengths: 3, 1"                          
[3] "target is character, current is numeric"

Final remark:

This is not a duplicate. I am interested in a solution that compares objects not numeric values

Comparison of the elements of a vector of numeric values: See existing solution on stackoverflow Test for equality among all elements of a single numeric vector

CodePudding user response：

You can try identical in sapply and compare each with the first element.

x <- list(list(1), list(1))
all(sapply(x[-1], identical, x[[1]]))
#[1] TRUE

x <- list(list(1), list(2))
all(sapply(x[-1], identical, x[[1]]))
#[1] FALSE

CodePudding user response：

Here is a function returning TRUE if all pairwise comparisons of the elements inside a list were identical:

all_pairs_equal <- function(elements) {
    all(mapply(function(x, y) identical(elements[x], elements[y]), 1, seq(1, length(elements))))
}

all_pairs_equal(list(iris, iris, iris))
#> [1] TRUE
all_pairs_equal(list(1, 1, 1))
#> [1] TRUE
all_pairs_equal(list(iris, iris, 2))
#> [1] FALSE

^{Created on 2021-10-05 by the reprex package (v2.0.1)}