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2d
comment General function for the expansion of a polynomial of operators
Yes—but in a comment the code does not format ...
2d
comment Implementation of a matrix formula
Nice solution. However, the OP did not make it clear why he wanted to re-implement a built-in function. Yes, I can read what he asked for—but he did not explain why. Since your code is only as fast as the built-in code (not surprisingly—it would be really impressive if it was faster), the only reason he could have would be to implement something closely related that is not built-in.
Feb
5
answered General function for the expansion of a polynomial of operators
Feb
5
awarded  Supporter
Jan
28
answered Implementation of a matrix formula
Jan
20
answered From built-in symbols to algebraic representation
Jan
13
comment Best way to emulate MATLAB's bsxfun using Map and similar functions
Can use Identity' instead of 1&.
Oct
12
awarded  Nice Question
Sep
17
answered Efficiently generating 2-D Gaussian random fields on the sphere
Sep
11
awarded  Yearling
Sep
10
answered SeriesData sucks when it can. How do I keep SeriesData from sucking?
Sep
7
awarded  Commentator
Sep
7
comment Find six vectors with rational entries under constraints?
You can split the 6x6 problem into two sets of 3, which is easier to satisfy (or a 4+2). The most general is 5+1 (where the 5 rows are independent). Instead of solving over rationals, you can work with integers (just multiply the 6x6 matrix of rationals by the LCD to obtain a matrix of integers).
Sep
5
comment Find six vectors with rational entries under constraints?
Perhaps you should state the full problem — and also where and how it arises. Note that, the conditions you stated require that the vectors must be linearly dependent (as the sum of each columns adds to zero). It is trivial to obtain the full solution for the 2x2 problem, and the 3x3 problem can be solved in terms of pythagorean triples.
Sep
3
revised Find six vectors with rational entries under constraints?
Added two references.
Sep
3
answered Find six vectors with rational entries under constraints?
Sep
3
answered How to make all cells be displayed in TraditionalForm
Aug
7
comment MMA breaks down when `DSolve` -ing a third-order linear ODE
I cannot see how the Weber function is LaplaceTransform-invariant, and I don't know what you mean about "in the physical sense". In the "mathematical sense" I played around in some special cases, and I looked in Tables of Laplace Transforms by Oberhettinger and Badii, which includes transforms of Weber functions, but your assertion is still not clear to me.
Aug
7
comment MMA breaks down when `DSolve` -ing a third-order linear ODE
I don't see how solutions to these equations, which appear to be unbounded for large Abs[x], could be LaplaceTransform-invariant functions. Do you have a reference for this?
Aug
4
answered MMA breaks down when `DSolve` -ing a third-order linear ODE