MATLAB: How to arrange an array elemets to unique pairs

Question

for example, X={'a1', 'b2', 'c3', 'd4'};

I want to rearrange X as below:

A={'a1'; 'a1'; 'a1'; 'b2';'b2'; 'c3' } B={'b2'; 'c3'; 'd4' ;'c3';'d4';'d4'}

that means A, B:

'a1' 'b2'

'a1' 'c3'

'a1' 'd4'

'b2' 'c3'

'b2' 'd4'

'c3' 'd4'

Then how to get A and B according to X?

Answer 1

X={'a1', 'b2', 'c3', 'd4'};
ii=1:numel(X)
jj=nchoosek(ii,2)
A=X(jj(:,1))'
B=X(jj(:,2))'