MATLAB: Looping each row from one matrix to the other matrix

for loopindexingismemberMATLAB

Hi.
I have two matrix with unique rows. Matrix A (228 x 9) and B(256 x 9) in one way or another have exact matching rows. I want to find the index where each row of B is a match of any row in A and store a new variable C (where all the indices are found). I tried matching manually per row of B against A. But it's taking me so long. I tried using for loop but I can't seem to figure out with ismember function.
Here's how I did it with single row from B.
[lia, locb] = ismember(A, B(1,:), 'rows'); % starting off from row 1.
Any help would be appreciated.
Cheers

Best Answer

You were close. Instead of referencing only 1 row of B, reference the entire matrix. 
[lia, locb] = ismember(A, B, 'rows');
Example
A = reshape(1:20,4,5);
B = A([3,1,4],:);  % B is a version of A with scattered rows and 1 row missing.
%     >> A
%     A =
%          1     5     9    13    17

%          2     6    10    14    18
%          3     7    11    15    19

%          4     8    12    16    20

%     >> B
%     B =
%          3     7    11    15    19
%          1     5     9    13    17
%          4     8    12    16    20
[lia, locb] = ismember(A, B, 'rows')
%     lia =
%       4×1 logical array
%        1


%        0
%        1
%        1
%     locb =
%          2
%          0
%          1
%          3
We can see that row 2 of A is not in B since lia(2)==0 and locb(2)==0.
We can also see that row 1 of A is in row 2 of B since locb(1)==2.
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