Merging two dissimilar matrix based on common row element

I have two arrays

A = 1  2.576
1   2.822
13  2.679
13  2.786
25  2.653
25  2.596
25  2.565

B= 1 nan
1   nan
1   nan
2   nan
2   nan
2   nan
..  nan
..  nan
13  nan
13  nan
13  nan
14  nan
14  nan
14  nan
..  nan
..  nan
20  nan
20  nan
20  nan
..  nan
..  nan
..  nan
25  nan
25  nan
25  nan

I have to create a third matrix C, which have all variables combined based on first column of B, while putting the values of A into it. The empty element, for which no values of A is available should be filled with nan. Desired output is matrix C.

C = 1  2.576
1   2.822
1   nan
2   nan
2   nan
2   nan
3   nan
3   nan
3   nan
4   nan
4   nan
4   nan
..  nan
..  nan
10  nan
10  nan
10  nan
13  2.679
13  2.786
14  nan
14  nan
14  nan
..  nan
..  nan
20  nan
20  nan
20  nan
25  2.653
25  2.596
25  2.565

I tried with intersect, however, it's not working for this case since the common column contains repeated values. Any help?

Answer 1

[Andrei Bobrov]

A = [1  2.576
1   2.822
13  2.679
13  2.786
25  2.653
25  2.596
25  2.565];

B = [kron((1:25)',[1;1;1]),nan(25*3,1)];

C = B;
p = findgroups(A(:,1));
AA = [A(:,1),cell2mat(accumarray(p,1,[],@(x){(1:numel(x))'}))];
q = findgroups(B(:,1));
BB = [B(:,1), cell2mat(accumarray(q,1,[],@(x){(1:numel(x))'}))];
C(ismember(BB,AA,'rows'),2) = A(:,2);

[Poulomi Ganguli]

Thanks! it works well.

[Jan]

@Poulomi Ganguli: If this solves your problem, please accept the answer.

Answer 2

[Jan]

Or with simple loops:

C  = B;
kC = 1;
nC = size(C, 1);
for iA = 1:size(A, 1)
   a = A(iA, 1);
   for iC = kC:nC
     if C(iC, 1) == a
       C(iC, 2) = A(iA, 2);
       kC       = iC + 1;
       break;   % Stop for iC loop
     end
   end
end