Convert a matrix to vector and back

 You must use byrow = FALSE (the default) to convert the vector back to a matrix.

> (d <- matrix(1:6, nrow=2, ncol=3))
     [,1] [,2] [,3]
[1,]    1    3    5
[2,]    2    4    6
> (v <- as.vector(d))
[1] 1 2 3 4 5 6
> matrix(v, nrow=2, ncol=3, byrow = FALSE)
     [,1] [,2] [,3]
[1,]    1    3    5
[2,]    2    4    6

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