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Feel free to correct the grammar mistakes in my posts.


1d
comment How to solve time dependent Optical Bloch Equations for a three level system?
Well, the ODEs are generated by some kind of matrix calculations, right? I'd rather you showed us the original one. Also, solving DEs in Mathematica is not simply a programming issue, a good understanding for the original problem is often necessary IMO. I think you'd better include some background information about your DEs.
1d
comment Improve the performance of solutions to Project Euler (#14)
What's the usage of s ?
1d
comment Problems with “Test Connectivity” and the Pacletserver
What's a "underlying user name"? Is there any evidence for its existence? I suspect the issue is not a user name with non-ASCII character, but some kind of unknown residuals. I faced very similar issue (even worse actually, I couldn't even call WolframAlpha or search words that are not function names) recently when updating v8 to v9, and I never used a non-ASCII user name. [Clean start](support.wolfram.com/kb/3274 ) doesn't work, but when I re-install my v9 in a new account, the problem resolved!
1d
comment Maple vs. Mathematica
@DanielLichtblau Er… Sorry for my poor English, but what's "epsilon credit"?
1d
comment Export[] performance
On my Vista 32bit, with v9.0.1, the timings are: {2.566000, "test.h5"} vs {3.374000, Null}
2d
comment Ted's explanation for the 3rd argument of ListCorrelate doesn't apply to the {1, -1} case?
@Tangshutao You're welcome, without answering your question, I won't have noticed the consistency today. 教学相长 :D
2d
comment Ted's explanation for the 3rd argument of ListCorrelate doesn't apply to the {1, -1} case?
@Tangshutao And I just noticed that in fact the rule used by Mathematica is just consistent with the rule used by tensor notation. If you've ever learned about the basic tensor notation in any course, just recall it and you'll find the rule of Dot no longer that hard to understand!
2d
comment Ted's explanation for the 3rd argument of ListCorrelate doesn't apply to the {1, -1} case?
@Tangshutao I think it's better not to. As far as I understand, instead of using concepts like "row", "column" etc. Mathematica uses Level of lists (Dimensions?) when discussing matrices, which leads to a rule that is a little different from what's usually used in our Linear Algebra text book. Dot of two lists are the match of the last dimension of the former list and the first dimension of the latter list, so {a, b, c} . {x, y, z} becomes valid, which in our text book should be written as {a, b, c} . {{x}, {y}, {z}} .
2d
comment How to understand the process of ListCorrelate when it in two-dimensional condition?
I just post a separate question for the confusing statement in Ted's document, you can have a look: mathematica.stackexchange.com/q/60101/1871
2d
comment How to understand the process of ListCorrelate when it in two-dimensional condition?
I just checked it, and found it confusing, if I understood the document well, the output should be True. Also, I think it'll be better to paste the part about the 4th argument here, or simply cut off the part below Generalizing beyond Times, Plus in your post, anyway, it's no longer related to your specific question.
2d
comment How to understand the process of ListCorrelate when it in two-dimensional condition?
Er… Why the output of the 4th picture is False? And where's the introduction for the usage of the 4th argument?
Sep
18
comment Numerical Solving Problem, PDE
Are you sure the analytic result should be like that?: q[x_, t_] = q0*Cos[k*x]*Cos[Sqrt[k^2 + 1]*t + delta]; FullSimplify[Derivative[0, 2][q][x, t] == -Derivative[2, 0][q][x, t] - q[x, t]]
Sep
17
comment Inconsistent linearity of inverse Fourier transform
I think it's not, at least I can't find an exact duplicate. Here's just a possible related one: mathematica.stackexchange.com/q/34027/1871
Sep
17
comment Inconsistent linearity of inverse Fourier transform
I guess you are in v8? I can reproduce this in this version. v9 and v10 give the correct result.
Sep
17
comment How to overwrite a private symbol value temporarily?
@qazwsx You can type " \` " instead of " ` " to make it display correctly inside the code block :)
Sep
17
comment How to overwrite a private symbol value temporarily?
@qazwsx I think there's no attribute named Unprotected, to clear the attribute Protected you can use Unprotect[Foo`Bar`Private`tmp] or ClearAttributes[Foo`Bar`Private`tmp, Protected] :)
Sep
16
comment How to overwrite a private symbol value temporarily?
What's the context of tmp? Suppose it's Global`, then how about tmp = 3; SetAttributes[tmp, Protected]; Get["mypackage.m"]? And tmp in a different context can be modified in a similar way.
Sep
16
comment Second order differential equation
BTW, as far as I can see, nonlinear boundary value ODEs has plagued this community for a long time. I just posted a question in scicomp.stackexchange, you can have a look.
Sep
16
comment Second order differential equation
Not easy, I should say. Here's an example. Depending on the nature of your equation, it's even impossible, I guess, because it's so sensible around w'[1]==0. Try this code: s = ParametricNDSolveValue[{w''[x] w'[x] + 3 w[x]^2 - 2 w[x] w'[x] == 0, w[1] == 0.8, w'[1] == a}, w, {x, 0, 1}, a]; Plot[s[a][0], {a, -1, 1}].
Sep
16
comment Second order differential equation
@AlbertRetey I think the v10 result isn't quite reliable. The same code can produce different result. For example, make the code fail by setting eps = 0.35 etc. and try eps = 0.75567 again, this time the code will fail. In some conditions I can even make it success but give different plots!