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Aug
24
comment Optimal partitioning of a graph
This appears to be cross-posted to Math.SE by a user of the same name, who then "answered" with yet another account because they "lacked enough reputation to comment".
Aug
20
reviewed Close Fine grained control over NGen-IC
Aug
19
comment Does the Lanczos starting vector have to be random?
@ChristianClason: One may have a sequence of problems to solve with slightly perturbed data.
Aug
17
reviewed No Action Needed Use scipy to get any vertex of polytope
Aug
11
reviewed Reviewed Efficiently extracting a submatrix in Matlab
Aug
11
comment Efficiently extracting a submatrix in Matlab
To build Msub without first building M suggests that you plan to rewrite code that does the latter to evaluate only certain rows of the matrix. Whether this can be done elegantly (not to say efficiently) depends on the way that the code to construct M works. For example, the construction of M might be recursive on columns, or in some other order not felicitous for extracting only certain rows.
Aug
11
reviewed Reviewed How to adjust scikit-learn FactorAnalysis() settings to get scores output similar to one from factanal() in R?
Aug
11
comment How to adjust scikit-learn FactorAnalysis() settings to get scores output similar to one from factanal() in R?
Various ways to estimate factor scores for the factor analysis model are possible. A smaller example might be a better starting point for tweaking the settings and describing how much agreement is sought or needed.
Aug
11
comment what is the upper bound of $\max \mathbf{w}^T\mathbf{x}_i$
As you have posed the problem, the choice of $\mathbf{z}$ cannot depend on $\mathbf{w}$ in any way. Indeed $\mathbf{z}$ is restricted to being a componentwise function $f$ of the entries of various $\mathbf{x}_i$, and the upper bound is required to hold for all $\mathbf{w}$. My example shows this is impossible.
Aug
11
answered what is the upper bound of $\max \mathbf{w}^T\mathbf{x}_i$
Aug
11
comment what is the upper bound of $\max \mathbf{w}^T\mathbf{x}_i$
What you want is impossible.
Aug
10
reviewed Reviewed what is the upper bound of $\max \mathbf{w}^T\mathbf{x}_i$
Aug
10
comment what is the upper bound of $\max \mathbf{w}^T\mathbf{x}_i$
This would be more straightforward if you knew the entries of w were nonnegative. Is that information available?
Aug
10
reviewed Reviewed Minimizing Cost Functions using Iterative Least Squares
Aug
10
comment Minimizing Cost Functions using Iterative Least Squares
Since $r$ is apparently a vector, you probably meant to ask if $||r||$, the norm of the residual, can be called "the cost of the system". As with $J$, cost is usually a scalar.
Aug
10
reviewed Close Are there any standardized file formats for point group character tables?
Aug
10
comment Are there any standardized file formats for point group character tables?
Here's a write-up of character tables from a molecular symmetry application: Understanding Character Tables of Symmetry Groups -- Chemwiki. From a software perspective we may well be in an era of "siloed development", but GAP Character Tables have been around awhile. The Question could be improved by adding context, e.g. what application of symmetry groups is intended.
Jul
25
reviewed Reviewed SVD of large block-hankel matrix
Jul
25
comment SVD of large block-hankel matrix
I suspect you are suggesting that for low-rank approximation, only the largest singular values are needed and can be found less expensively than the full decomposition. However your brief post leaves much to the Readers imagination.
Jul
25
reviewed Reviewed Modern C++ in scientific computing?