Given an arbitrary symmetric NbyN matrix A, how can its original values be calculated from $P$?
$$ P = A'A$$
Both $A$ and $P$ have \( \frac{N^2N}{2}+N \) degrees of freedom.
Edit: added the constraint that A is symmetric
Given an arbitrary symmetric NbyN matrix A, how can its original values be calculated from $P$? $$ P = A'A$$ Both $A$ and $P$ have \( \frac{N^2N}{2}+N \) degrees of freedom. Edit: added the constraint that A is symmetric 

closed as too localized by Will Jagy, Yemon Choi, Loop Space, S. Carnahan♦ Feb 27 '12 at 10:10This question is unlikely to help any future visitors; it is only relevant to a small geographic area, a specific moment in time, or an extraordinarily narrow situation that is not generally applicable to the worldwide audience of the internet. For help making this question more broadly applicable, visit the help center.If this question can be reworded to fit the rules in the help center, please edit the question. 


Well, that depends on the ground field.


