将大矩阵分成子集，R

Question

I would like to make subgroups for a matrix， and each subgroup contains the same amount of column. For example, there is a matrix with 1000 rows and 420 columns, and I would like to split into 35 sub-matrix in order, like first one contains the first 12 cols, and the second contains the second 12 cols, and so on. I think I could use function Iris. Please help me!

iris[c()]

Answer 1

Not sure if this is what you're after, but here's a reproducible example:

# Define matrix
M = matrix( 
     c(1:20), 
     nrow=2, 
     ncol=10) 

# Split into 5 submatrices of equal size
lapply(split(M, rep(1:5, each = 4)), matrix, ncol = 2)
$`1`
     [,1] [,2]
[1,]    1    3
[2,]    2    4

$`2`
     [,1] [,2]
[1,]    5    7
[2,]    6    8

$`3`
     [,1] [,2]
[1,]    9   11
[2,]   10   12

$`4`
     [,1] [,2]
[1,]   13   15
[2,]   14   16

$`5`
     [,1] [,2]
[1,]   17   19
[2,]   18   20

Answer 2

You can turn your 1000 × 420 matrix into a 1000 × 12 × 35 matrix with

dim(x) <- c(1000, 12, 35)

where x is the original matrix. Then x[, , 1] gives you the first 1000 × 12 sub-matrix, x[, , 2] the second sub-matrix, and so forth.