How to use identical function to compare list of matrices by the row

  • A+

Suppose I have a list of two matrices, x and y.

 x <- c(3,4,5,5, 3,4,5,6, 5,6,2,1)  x <- matrix(x,3,4)  y <- c(3,4,5,5, 3,4,5,6, 5,5,2,1)  y <- matrix(y,3,4)  d <- list(x, y)  > x      [,1] [,2] [,3] [,4] [1,]    3    5    5    6 [2,]    4    3    6    2 [3,]    5    4    5    1  > y      [,1] [,2] [,3] [,4] [1,]    3    5    5    5 [2,]    4    3    6    2 [3,]    5    4    5    1 

I would like to compare each row of these two matrices using the identical function. Here, the two matrices are the same unless for the last element of the first row.

How could I compare these two matrices, row by row? Any help, please?

My tried is:

res <- round(apply(array(unlist(d), c(4, 4, 4)), c(1,2), identical),2) 

(from there "I tried the code used here)

But I have got an error:

Error in FUN(newX[, i], ...) : argument "y" is missing, with no default

Please note that the element of the list is arbitrary. That is, sometimes, I have only 2 matrices, however, another time may I have 6 matrices

The expected output should be like this

output:      [,1] [,2] [,3] [,4] [1,]    TRUE    TRUE    TRUE    FALSE [2,]    TRUE    TRUE    TRUE    TRUE [3,]    TRUE    TRUE    TRUE    TRUE 


1) This defines Identical to be a function which returns TRUE if all its arguments are identical. It does this by computing the sd of its arguments and comparing that to zero. The second line of code applies this to the corresponding elements of the matrices.

Identical <- function(...) sd(c(...)) == 0 array("mapply", c(Identical, d)), dim(d[[1]])) 


     [,1] [,2] [,3]  [,4] [1,] TRUE TRUE TRUE FALSE [2,] TRUE TRUE TRUE  TRUE [3,] TRUE TRUE TRUE  TRUE 

A few alternate ways to define Identical. These have the advantage that they work with non-numeric matrices as well. The second one uses identical as requested.

Identical <- function(...) all(c(...)[-1] == ..1)  Identical <- function(...) all(sapply(c(...)[-1], identical, ..1)) 

2) This alternate method is only one line of code and uses the whole object approach with no explicit use of dimensions or indexes. It unlists d and applies sd over corresponding elements of that using tapply. Finally it compares that to zero.

tapply(unlist(d), list(sapply(d, row), sapply(d, col)), sd) == 0 

2a) A variation is to define the comparison as a separate function:

Same <- function(x) sd(x) == 0 tapply(unlist(d), list(sapply(d, row), sapply(d, col)), Same) 

That makes it easier to define alternatives by redefining Same such as the following where the second definition uses identical.

Same <- function(x) all(x[-1] == x[1])  Same <- function(x) all(sapply(x[-1], identical, x[1])) 


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