Combine and sorting array values

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L. Edwin M.
L. Edwin M. on 13 Apr 2022
Commented: L. Edwin M. on 16 Apr 2022
Hello!
I got a result matrix A
A = [3 9 4]
And another matrix B
[ 3 8
4 8
15 5
B= 16 1
16 2
16 7
17 6
17 2 ]
First i want to combine A with all values of the second column of B that have a unique value in the first column -> Matrix AB
AB = [3 9 4 8 5]
As a final result i want the combinations of AB with all values of the second column of B that have not a unique value in the first column ->Result
Result= [3 9 4 8 5 1 6 3 9 4 8 5 1 2
3 9 4 8 5 2 6 3 9 4 8 5 2 2
3 9 4 8 5 7 6 3 9 4 8 5 7 2]
How can i do that?
Many thanks in advance!

Accepted Answer

DGM
DGM on 13 Apr 2022
Edited: DGM on 13 Apr 2022
Maybe something like:
A = [3 9 4];
B = [3 8
4 8
15 5
16 1
16 2
16 7
17 6
17 2];
U = unique(B(:,1));
c = histcounts(B(:,1),U);
col1unique = ismember(B(:,1),U(c==1));
AB = [A unique(B(col1unique,2),'stable').']
AB = 1×5
3 9 4 8 5
combpool = unique(B(~col1unique,2));
combs = nchoosek(combpool,2);
result = [repmat(AB,[size(combs,1) 1]) combs]
result = 6×7
3 9 4 8 5 1 2 3 9 4 8 5 1 6 3 9 4 8 5 1 7 3 9 4 8 5 2 6 3 9 4 8 5 2 7 3 9 4 8 5 6 7
If you want the result formatted as shown, then:
result = reshape(result.',size(result,2)*2,[]).'
result = 3×14
3 9 4 8 5 1 2 3 9 4 8 5 1 6 3 9 4 8 5 1 7 3 9 4 8 5 2 6 3 9 4 8 5 2 7 3 9 4 8 5 6 7
  6 Comments
DGM
DGM on 16 Apr 2022
Oh I misunderstood what kind of combinations you were after. I was just doing combinations of all remaining (unique) elements of col2.
This does combinations of the groups within col2 associated with the nonunique blocks in col1
A = [3 9 4];
B = [3 8
4 8
15 5
16 1
16 2
16 7
17 6
17 2];
[c ed] = histcounts(B(:,1),'binmethod','integers');
col1unique = ismember(B(:,1),ed(c==1)+0.5);
AB = [A unique(B(col1unique,2),'stable').']
AB = 1×5
3 9 4 8 5
% split col2 of B into groups associated with nonunique elements of col1
Bnonu = B(~col1unique,:);
g = findgroups(Bnonu(:,1));
ngroups = max(g);
elements = cell(1,ngroups);
for k = 1:ngroups
elements{k} = Bnonu(g==k,2);
end
% find combinations of elements between groups
combinations = cell(1,ngroups); %set up the varargout result
[combinations{:}] = ndgrid(elements{:});
combinations = cellfun(@(x) x(:), combinations,'uniform',false);
result = [combinations{:}];
result = [repmat(AB,[size(result,1) 1]) result]
result = 6×7
3 9 4 8 5 1 6 3 9 4 8 5 2 6 3 9 4 8 5 7 6 3 9 4 8 5 1 2 3 9 4 8 5 2 2 3 9 4 8 5 7 2
based on this:

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