MATLAB: Extract values common to 5 columns

homeworkMATLAB

Hi, I have a matrix A with 5 columns (1 to 5). I want to compare columns 1 through 5 and then extract values common to all 5 columns. Put the extracted values (common to all 5 columns) into a separate matrix called Match. Thank you!

Best Answer

Since it is not homework, see if this does what you want: 
A = randi(9,20,5);                                      % Create Matrix (Integers For Simplicity)
[Au,ia,ic] = unique(A);                                 % Unique Elements (Use ‘uniquetol’ For Non-Integers)
[~,c] = ind2sub(size(A), (1:numel(A)).');               % Create Vector Of Column Indices
Tally = accumarray(ic,c,[],@(x){Au(x)});                % Accumulate By Column
ColsWithAu = cellfun(@(x)nnz(ismember(Au,x)), Tally);   % Return Columns With Specific Elements
Common = Au(ColsWithAu==5)                              % If Element Appears In Every Column, It Is Common To All Columns
It worked for my test matrix.
If your rmatrix has floating-point elements, use uniquetol instead of unique. You will need to choose the appropriate tolerance value.
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