How to find all possible combinations between the numbers of two vectors where order does matter

I have the following two vectors

a = [1 2 3 4]
b = [2 4]

and I would like to find all possible combination between the numbers of these two vectors, but order does matter. So a valid combination would be [1 2] as well as [2 1], thus yielding two results for each of those cases. So using my vectors a and b what I would like to get is:

c = [2 1
    2 2
    2 3
    2 4
    4 1
    4 2
    4 3
    4 4
    1 2
    1 4
    3 2
    3 4] ;

Notice that rows 1:8 on the above can be returned by using either combvec(a, b), or the simple method:

[m, n] = ndgrid(a, b) ;
 Z = [m(:), n(:)] 

However I am struggling to find out how to make a code to create the last four rows. Thanks for your help in advance

Answer 1

[the cyclist]

I expect there is a more efficient way, but I think this will do what you want.

a = [1 2 3 4];
b = [2 4];

c = unique([combvec(a,b)'; combvec(b,a)'],'row');
disp(c)

     1     2
     1     4
     2     1
     2     2
     2     3
     2     4
     3     2
     3     4
     4     1
     4     2
     4     3
     4     4

[KostasK]

yep, that works!