[R] matrix of bins with different length

[Balazs Torma]

Dear users,

    please help to define the following data structure:

I would like to have a matrix, where every element is a container of  
different size , containing real numbers. The containers (bins) are  
addressed by an index pair [i,j] (i is number of corresponding row of  
the matrix, j is the coloumn of the matrix). The containers are  
initially empty, I would like to fill them dynamically (put certain  
numbers into different bins in each iteration).

I can not define a 3 dimensional array, because I don't know the  
length of the third dimension in advance, and because the vectors  
(containers) in the matrix are usually of different length.

Any help greatly appreciated,
Balazs Torma