MATLAB: Shifted triangular matrix array

Question

If I have matrix a=[1 2; 3 4; 5 6; 7 8] (dimension 4×2) and i want to calculate

A= [1 2 0 0 0 0 0 0;

3 4 1 2 0 0 0 0;

5 6 3 4 1 2 0 0;

7 8 5 6 3 4 1 2]

(dimension 4×8),

how can i do?

Thanks.

Answer 1

ac=num2cell([0,0;a],2); 
T=toeplitz(1:4,[1,zeros(1,3)]);
A=cell2mat(ac(T+1))
A =
     1     2     0     0     0     0     0     0
     3     4     1     2     0     0     0     0
     5     6     3     4     1     2     0     0
     7     8     5     6     3     4     1     2