[R] replicate matrix blocks different numbers of times into new matrix

[Ralph S.]

Hi,

I am trying to replicate blocks of a matrix (defined by factors) into another matrix, but an unequal, consecutive number of times for each factor. 

I need to find an elegant and fast way to do this, so loops will not work.

An example of what I am trying to do is the following:

# the data - first column entries are both data and the two factors
x<-matrix(c(1,2,3,4),2,2)
> x
     [,1] [,2]
[1,]    1    3
[2,]    2    4

# the number of repetitions of the first and second factor
n<-c(1,3)

This is what I want as output:

     [,1] [,2]
[1,]    1    3
[2,]    2    4
[3,]    2    4
[4,]    2    4


Any ideas how to get there? I have tried using tapply with combination of rep, but this does not work (I need 1 and then 3 replications).

Any help would be great!

-Ralph



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