MATLAB: How to interchange the elements of a vector/matrix

Question

hi

a,b,c,d all are 2×1 matrices.

i will run a for loop and with each loop the elements of matrix x will increase.

example-

for i=1, x=[a1]

for i=2, x=[a1 b1 b2]

for i=3, x=[a1 b1 b2 c1 c2 c3 c4]

for i=3 x=[a1 b1 b2 c1 c2 c3 c4 d1 d2 d3 d4 d5 d6 d7 d8]

now after i=2, i want to rearrange the matrix to look like

y=[b1 a1 b2].

after i=3, i want to rearrange the matrix to look like

y=[c1 b1 c2 a1 c3 b2 c4]

after i=4, i want to rearrange the matrix to look like

y= [d1 c1 d2 b1 d3 c2 d4 a1 d5 c3 d6 b2 d7 c4 d8].

please tell me how i can do this?

basically all the new elements will be placed in between the existing elements.

Answer 1

This works:

for k = 1:4
    % fake data:
    new = zeros(2,pow2(k-1));
    new(:) = 10*k+(1:numel(new));
    % zip data together:
    if k==1
        out = new
    else
        out = [reshape([new(:,1:end-1);out],2,[]),new(:,end)]
    end
end

It displays this in the command window:

out =
   11
   12
out =
   21   11   23
   22   12   24
out =
   31   21   33   11   35   23   37
   32   22   34   12   36   24   38
out =
   41   31   43   21   45   33   47   11   49   35   51   23   53   37   55
   42   32   44   22   46   34   48   12   50   36   52   24   54   38   56