MATLAB: Setting non-repeated elements from two related matrices to NaN

MATLABmatrix manipulation

For the matrices A and B,
    A = [1 2 1; 3 5 1; 2 3 6]
    B = [1 2 3; 4 5 6; 7 8 9]
set the non-repeated elements of A to NaN, setting also to NaN the related elements of B. By non-repeated elements I refer to elements that only occur once through the whole matrix. Generate the two new matrices from those:
    A_nan = [1 2 1; 3 NaN 1; 2 3 NaN]
    B_nan = [1 2 3; 4 NaN 6; 7 8 NaN]
Thank so much in advance, just trying to manipulate the matrix before a Regression between A and B.

Best Answer

A = [1 2 1; 3 5 1; 2 3 6];
B = [1 2 3; 4 5 6; 7 8 9];
uniqueA = unique(A);
counts = histcounts(A,[uniqueA;Inf]);
nanIndex = ismember(A,uniqueA(counts==1));
A(nanIndex) = NaN;
B(nanIndex) = NaN;
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