I have some data that has the following dimension
[100, 2, 100]. It represents 100 rows of observations, 2 columns of variables, repeated in 100 experiments.
I would like to have the data in a matrix with the dimensions [10000, 2], where I have effectively eliminated the concept of experiments.
Something like .reshape in python.
I found the reshape package. However I wonder if it can be done without it.
Is there a more elegant way to do this in base R than a for loop?
>Solution :
Let’s start from a smaller example with array m
m <- array(rep(1:100, 5), c(10, 2, 5))
which is a 3-D array
> m
, , 1
[,1] [,2]
[1,] 1 11
[2,] 2 12
[3,] 3 13
[4,] 4 14
[5,] 5 15
[6,] 6 16
[7,] 7 17
[8,] 8 18
[9,] 9 19
[10,] 10 20
, , 2
[,1] [,2]
[1,] 21 31
[2,] 22 32
[3,] 23 33
[4,] 24 34
[5,] 25 35
[6,] 26 36
[7,] 27 37
[8,] 28 38
[9,] 29 39
[10,] 30 40
, , 3
[,1] [,2]
[1,] 41 51
[2,] 42 52
[3,] 43 53
[4,] 44 54
[5,] 45 55
[6,] 46 56
[7,] 47 57
[8,] 48 58
[9,] 49 59
[10,] 50 60
, , 4
[,1] [,2]
[1,] 61 71
[2,] 62 72
[3,] 63 73
[4,] 64 74
[5,] 65 75
[6,] 66 76
[7,] 67 77
[8,] 68 78
[9,] 69 79
[10,] 70 80
, , 5
[,1] [,2]
[1,] 81 91
[2,] 82 92
[3,] 83 93
[4,] 84 94
[5,] 85 95
[6,] 86 96
[7,] 87 97
[8,] 88 98
[9,] 89 99
[10,] 90 100
If you want to reshape it into a 50x2 array, we can try
> apply(m, 2, `[`)
[,1] [,2]
[1,] 1 11
[2,] 2 12
[3,] 3 13
[4,] 4 14
[5,] 5 15
[6,] 6 16
[7,] 7 17
[8,] 8 18
[9,] 9 19
[10,] 10 20
[11,] 21 31
[12,] 22 32
[13,] 23 33
[14,] 24 34
[15,] 25 35
[16,] 26 36
[17,] 27 37
[18,] 28 38
[19,] 29 39
[20,] 30 40
[21,] 41 51
[22,] 42 52
[23,] 43 53
[24,] 44 54
[25,] 45 55
[26,] 46 56
[27,] 47 57
[28,] 48 58
[29,] 49 59
[30,] 50 60
[31,] 61 71
[32,] 62 72
[33,] 63 73
[34,] 64 74
[35,] 65 75
[36,] 66 76
[37,] 67 77
[38,] 68 78
[39,] 69 79
[40,] 70 80
[41,] 81 91
[42,] 82 92
[43,] 83 93
[44,] 84 94
[45,] 85 95
[46,] 86 96
[47,] 87 97
[48,] 88 98
[49,] 89 99
[50,] 90 100