vec <- c( 1, 2, 3, 4, 11, 22, 33, 44, 111, 222, 333, 444) matrix(vec) # # [,1] # [1,] 1 # [2,] 2 # [3,] 3 # [4,] 4 # [5,] 11 # [6,] 22 # [7,] 33 # [8,] 44 # [9,] 111 # [10,] 222 # [11,] 333 # [12,] 444 matrix(vec, nrow=3) # # [,1] [,2] [,3] [,4] # [1,] 1 4 33 222 # [2,] 2 11 44 333 # [3,] 3 22 111 444 matrix(vec, nrow=3, byrow = TRUE) # # [,1] [,2] [,3] [,4] # [1,] 1 2 3 4 # [2,] 11 22 33 44 # [3,] 111 222 333 444