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 Dec 4 awarded Popular Question Jun 15 awarded Popular Question Jul 2 awarded Curious Nov 14 awarded Teacher Nov 14 comment Exclude an RGB color from a set This is probably best asked in a Machine Learning group, I would suggest trying the stats stack exchange site. What you're looking for is a clustering algorithm, to accept the data points that are close together in your space, and reject outliers. This can be a tricky problem, and the stats people will have a much better background for answering your question than just pure mathematics. Nov 14 asked Product of positive definite matrices not itself positive definite May 17 comment Derivative of conjugate transpose of matrix You've worked hard for this acceptance, thank you for your effort! May 17 accepted Derivative of conjugate transpose of matrix May 16 awarded Commentator May 16 comment Derivative of conjugate transpose of matrix This seems like it's kind of cheating though..... :P I see you've gotten the "correct" answer, but modifying an entry in $W$ will certainly modify it in $W^H$ and vice versa, therefore I don't see how we can ignore one or the other as a "constant" May 16 asked Derivative of conjugate transpose of matrix May 14 comment Solving for a matrix from its quadratic form I get it! Thank you so much! May 14 accepted Solving for a matrix from its quadratic form May 14 comment Solving for a matrix from its quadratic form Also, because the $vec(Z)$ operation transforms from a matrix to a vector, must we still use the Frobenius norm notation $\| \cdot \|_F$? It should be functionally equivalent to the $\ell^2$ norm again, right? May 14 comment Solving for a matrix from its quadratic form Excellent. This is exactly what I needed. I had apriori knowledge that $W = YX^H (X X^H)^{-1}$ but I could not figure out how to get there from the problem statement. I don't fully understand your answer, so I'd like to ask some questions. I understand your expansion with Kronecker products and such, but I don't understand how you isolate $vec(W)$ on the left hand side. I get the last conversion from Kronecker products back to plain matrix multiplication, but I have a hard time pulling things apart in my head for the step before that. Can you help me work that out? May 14 comment Solving for a matrix from its quadratic form This is a good insight. I'm going to go think about it! If I decide that I need help with this new formulation, should I open a new question, or edit this one appropriately? And thank you for your help! May 14 comment Solving for a matrix from its quadratic form An excellent point. I have updated my answer to explain why this question is slightly better posed. Essentially, I have multiple $x$ and $y$ vectors that I can bring in to help narrow the problem down. May 14 revised Solving for a matrix from its quadratic form Explained that I have multiple sets of vectors, therefore the W matrix is not as underdetermined as previously thought May 14 asked Solving for a matrix from its quadratic form Mar 3 awarded Supporter