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 Sep 10 awarded Popular Question Nov 6 comment Minimizing maximum absolute column sum norm of the residual between a matrix and its $k$-rank approximation Thank you very much for the comment. Actually, this was the problem we were discussing in our reading group. That's why I wanted to learn if there's an already known way to solve it. Oct 31 revised Minimizing maximum absolute column sum norm of the residual between a matrix and its $k$-rank approximation added 12 characters in body; edited tags Oct 27 awarded Tumbleweed Oct 20 asked Minimizing maximum absolute column sum norm of the residual between a matrix and its $k$-rank approximation Aug 29 awarded Yearling Jun 10 accepted $l_1$ distance of a point to a convex polygon Jun 9 asked $l_1$ distance of a point to a convex polygon Feb 3 awarded Nice Question Jan 2 comment What does it mean to select $O(k \log k / \epsilon^2)$ indices? Actually, I know Big-O notation and asymptotic analysis well. But this is a different case. In algorithm analysis, we compute the complexity given the array has size N. For example we may have 2 additions in a loop, then the result will be 2 times the loop count. It is OK. Coefficient 2 is not leading here and we are not setting something to the complexity here. But in the question, I need to set some variable which is computed in Big-O notation. This is confusing part. Jan 2 comment What does it mean to select $O(k \log k / \epsilon^2)$ indices? I think I will go for this. Dec 30 asked What does it mean to select $O(k \log k / \epsilon^2)$ indices? Dec 4 awarded Scholar Dec 4 accepted Sum of derivatives of a polynomial Dec 4 awarded Editor Dec 4 revised Sum of derivatives of a polynomial edited title Dec 4 asked Sum of derivatives of a polynomial Nov 20 awarded Benefactor Nov 20 comment Exciting games and material to motivate children to math I gave +1 for all answers, which are very good recommendations. But I gave the bounty for this answer since it had the most upvotes and was very amazing. As a note, I didn't accept any answer to welcome further contributions since any upcoming answer may help to instructors who want to have a similar lecture with the kids. Nov 18 awarded Nice Question