Setting non-repeated elements from two related matrices to NaN

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.

Answer 1

[the cyclist]

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;

[Victor Francisco Pajuelo Madrigal]

Thank you very much, this is precisely what I was looking for! Clear and beautiful code, helps me to speed up the learning process. Thanks!