From a statistics point of view (ignoring your Perl question alltogether), I would put 1.0 on the diagonal of the missing lines and columns to ensure that the augmented matrix is a correlation matrix again. This would also help to maintain the status as a correlation matrix when doing weighted averages across matrices.

Generally, a lot of things can go wrong when manipulating large correlation matrices.

In reply to Re: combining multiple matrices with placeholders if row and column values in one matrix do not exist in another by hdb
in thread combining multiple matrices with placeholders if row and column values in one matrix do not exist in another by mulder4786

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