random data matrix - r

Question

How to randomize values in an R matrix
For example, here is what I Would like to randomize
A, A, A, A, A
B, B, B, B, B
C, C, C, C, C
D, D, D, D, D
E, E, E, E, E
F, F, F, F, F
G, G, G, G, G

Answer 1

I'd recommend a random process that checks for dupes and reruns columns as needed.
myfunc <- function(nrow = 7, ncol = 4, iters = 500) {
m <- matrix("", nrow = nrow, ncol = ncol)
len <- seq_len(nrow)
m[,1] <- sample(LETTERS[len])
iter <- 0
for (col in seq_len(ncol)[-1]) {
iter <- iter + 1
if (iter > iters) break
m[,col] <- sample(LETTERS[len])
while (any(m[,col] == m[,-col])) {
iter <- iter + 1
if (iter > iters) break
m[,col] <- sample(LETTERS[len])
}
}
attr(m, "iter") <- iter
m
}
set.seed(42)
myfunc()
# [,1] [,2] [,3] [,4]
# [1,] "A" "B" "F" "D"
# [2,] "E" "G" "A" "C"
# [3,] "G" "C" "B" "A"
# [4,] "F" "A" "C" "G"
# [5,] "B" "D" "E" "F"
# [6,] "C" "E" "D" "B"
# [7,] "D" "F" "G" "E"
# attr(,"iter")
# [1] 69
I added the internal iter counting just so that we'd know how many times it took. And I added the iters limit so that it would not go on forever with ridiculous combinations; you'll know it hit the limit when one or more columns are empty strings "":
myfunc(7,7)
# [,1] [,2] [,3] [,4] [,5] [,6] [,7]
# [1,] "D" "E" "G" "B" "A" "C" "G"
# [2,] "B" "A" "D" "G" "E" "F" "C"
# [3,] "C" "D" "F" "A" "G" "E" "E"
# [4,] "E" "B" "C" "D" "F" "A" "B"
# [5,] "F" "G" "E" "C" "B" "D" "F"
# [6,] "A" "C" "B" "F" "D" "G" "A"
# [7,] "G" "F" "A" "E" "C" "B" "D"
# attr(,"iter")
# [1] 501
myfunc(7,7)
# [,1] [,2] [,3] [,4] [,5] [,6] [,7]
# [1,] "D" "E" "C" "F" "G" "B" ""
# [2,] "G" "D" "E" "A" "F" "C" ""
# [3,] "F" "A" "B" "G" "D" "A" ""
# [4,] "E" "B" "F" "D" "C" "D" ""
# [5,] "A" "C" "G" "B" "E" "E" ""
# [6,] "C" "F" "A" "E" "B" "F" ""
# [7,] "B" "G" "D" "C" "A" "G" ""
# attr(,"iter")
# [1] 502

Answer 2

Your shifting approach you may realize like so.
mapply(function(x, y) x[(seq(x) + y - 1) %% nrow(m)], as.data.frame(m), 1:ncol(m))
# V1 V2 V3 V4
# [1,] "A" "B" "C" "D"
# [2,] "B" "C" "D" "E"
# [3,] "C" "D" "E" "F"
# [4,] "D" "E" "F" "A"
# [5,] "E" "F" "A" "B"
# [6,] "F" "A" "B" "C"
Data:
m <- structure(c("A", "B", "C", "D", "E", "F", "G", "A", "B", "C",
"D", "E", "F", "G", "A", "B", "C", "D", "E", "F", "G", "A", "B",
"C", "D", "E", "F", "G"), .Dim = c(7L, 4L))

Answer 3

To get a deterministic permutation, create the matrix and fill it in using the row() and col() functions. For example,
rotated <- function(r, c, symbols = NULL) {
num <- max(r, c)
m <- matrix(NA, r, c)
m <- (row(m) + col(m) - 2) %% num + 1
if (!is.null(symbols)) {
m <- symbols[m]
dim(m) <- c(r,c)
}
m
}
rotated(7, 4, LETTERS)
#> [,1] [,2] [,3] [,4]
#> [1,] "A" "B" "C" "D"
#> [2,] "B" "C" "D" "E"
#> [3,] "C" "D" "E" "F"
#> [4,] "D" "E" "F" "G"
#> [5,] "E" "F" "G" "A"
#> [6,] "F" "G" "A" "B"
#> [7,] "G" "A" "B" "C"
Created on 2020-10-07 by the reprex package (v0.3.0)
If you want it randomized, permute rows and columns randomly:
rotated(7, 4, LETTERS)[sample(7), sample(4)]
#> [,1] [,2] [,3] [,4]
#> [1,] "B" "D" "C" "A"
#> [2,] "F" "A" "G" "E"
#> [3,] "E" "G" "F" "D"
#> [4,] "A" "C" "B" "G"
#> [5,] "G" "B" "A" "F"
#> [6,] "C" "E" "D" "B"
#> [7,] "D" "F" "E" "C"