I have a matrix m, which I would like to convert into a list l of submatrices consisting of x rows of m.
m <- matrix(sample(15, 60, TRUE), 12)
l <- list(m[1:3,], m[4:6,], m[7:9,], m[10:12,])
I'm certain that there's a simple and more generic solution (full vectorised?) to this, but still being new to R I cannot find it.
I thought about using lapply, but don't really know how.
Just proceed as you did in your question using Map to iterate on the beginning index and finishing index:
p = 3
Map(function(u,v) m[u:v,], seq(1,nrow(m),p), seq(p,nrow(m),p))
#[[1]]
# [,1] [,2] [,3] [,4] [,5]
#[1,] 14 8 5 10 9
#[2,] 10 4 5 7 8
#[3,] 3 3 6 7 3
#[[2]]
# [,1] [,2] [,3] [,4] [,5]
#[1,] 4 8 12 1 1
#[2,] 4 2 13 1 11
#[3,] 6 2 4 1 12
#[[3]]
# [,1] [,2] [,3] [,4] [,5]
#[1,] 11 12 8 5 7
#[2,] 3 6 2 6 2
#[3,] 13 13 10 7 12
#[[4]]
# [,1] [,2] [,3] [,4] [,5]
#[1,] 9 7 12 8 9
#[2,] 10 8 13 14 13
#[3,] 12 6 11 4 11