How to make Duplicate values

I have matrix 1 example : W = [4 2 8 1 2 6 3 5 9]

and now matrix 2 example : Q = [1 2 1 2 3 2 1 2 1];

How to make duplicate W with Q values. And I want to get final matrix as R = [4 2 2 8 1 1 2 2 2 6 6 3 5 5 9]

please help me

[per isakson]

Search the FEX for run length encoding

Answer 1

[Roger Stafford]

   p = cumsum(accumarray(cumsum([1,Q])',1))';
   R = W(p(1:end-1));

Note: If you have a zero in Q, the corresponding W value won't be copied at all in R.

[Andhika Fajar]

Thank u Roger Stafford. its work

Answer 2

[Geoff Hayes]

Andhika - given your above example, you want to replicate each element in W for the number of times given in Q. So, for example, Q(1) is 1, and so W(1) is replicated once. More generally, W(k) is replicated Q(k) times. The arrayfun is a good to use as we can apply our "replicating" function to each of the k pairs as

 result = cell2mat(arrayfun(@(w,q)repmat(w,1,q),W,Q,'UniformOutput',false));

We create a function that takes two inputs, the kth value from W as w, and the kth value from Q as q, then use repmat to replicate the w a q number of times. As the result is a cell (row) array, we convert it from a cell array to a matrix (row) using cell2mat.

Using your example W and Q vectors, we see that result is

 W      = [4 2 8 1 2 6 3 5 9];
 Q      = [1 2 1 2 3 2 1 2 1];
 result = cell2mat(arrayfun(@(w,q)repmat(w,1,q),W,Q,'UniformOutput',false))

 result =

     4  2  2  8  1  1  2  2  2  6  6  3  5  5  9

[Andhika Fajar]

Thank u Geoff Hayes. its work too