MATLAB: Merge vector and matrix with duplicated common values

Question

I have a large size of matrix and here is the sample. I have an another vector,B.

 A = 
  1  1  2  3  …
  1  2  3  5  
  1  3  4  2  
  2  4  5  5  
  2  5  1  6  
  2  6  4  3  
  3  7  5  1  
  3  7  3  2  
  3  8  2  1  
  4  9  5  4  
  4  9  6  1  
  4  0  2  5  
...
B = 
1
2
1
1

I would like to merge the vector and the matrix by matching first column of A and the vector B. Because there are multiple rows with the each value of first column (e.g., 4 rows for value 1, 3 rows of value 2 and so on), all of rows for each value should be merged for a new dataset (C as below), and duplicated value in vector B (as shown, 1 is duplicated), it seems to be challenging.

Here is what I want to have

C = 
 1  1  2  3
1  2  3  5
1  3  4  2
2  4  5  5
2  5  1  6
2  6  4  3
1  1  2  3
1  2  3  5
1  3  4  2
1  1  2  3
1  2  3  5
1  3  4  2

Answer 1

One solution using accumarray:

>> A = [1,1,2,3;1,2,3,5;1,3,4,2;2,4,5,5;2,5,1,6;2,6,4,3;3,7,5,1;3,7,3,2;3,8,2,1;4,9,5,4;4,9,6,1;4,0,2,5];
>> B = [1;2;1;1];
>> R = 1:size(A,1);
>> Z = accumarray(A(:,1),R.',[],@(r){A(r,:)});
>> C = vertcat(Z{B})
C =
     1     1     2     3
     1     2     3     5
     1     3     4     2
     2     4     5     5
     2     5     1     6
     2     6     4     3
     1     1     2     3
     1     2     3     5
     1     3     4     2
     1     1     2     3
     1     2     3     5
     1     3     4     2