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Feb
23
awarded Nice Answer
Feb
20
comment Can Mathematica's random number generation be improved?
I wouldn't say that Mathematica isn't good for writing simulations in general, but when you don't want to do any of the numerical implementation yourself, you are of course at the mercy of the standard library. It's to be expected that different packages have different strengths and weaknesses here. It also depends very strongly on the specific algorithm (although Mathematica is probably worse than most languages in terms of its extreme sensitivity to coding style--things like Julia may be better). I like Mathematica and I use it a lot, but it simply can't be the best tool for every job.
Feb
20
comment Align stars in multiple images
I have tried this before and I didn't find it very easy in Mathematica. My suggestion would be to use some specialized software like DeepSkyStacker, where someone has already figured out the details for you.
Feb
20
comment Can Mathematica's random number generation be improved?
I don't really agree with rasher's answer, but I do think it's fair to point out that Mathematica's focus is usually on generality over run-time efficiency. The per-call overhead is often very high, especially for those functions implemented in terms of top-level code. This shouldn't necessarily be excused, but it is a fact one needs to know. One could read the R or Octave source code and reproduce the same implementation in *Mathematica*--clearly R is doing something clever if it can beat C++. Or, if this isn't very appealing, RLink and MATLink would allow you to call R or MATLAB directly.
Feb
19
comment Can Mathematica's random number generation be improved?
I think that if blochwave's answer is not that appealing to you, then you probably came to the wrong place to raise this concern. Although I agree with you that these functions seem to be unfeasibly slow (especially in comparison to R, which is not known for its speed), the fact is that there's really nothing we as users can do about it. So, if this still seriously concerns you even though workarounds are available, I'd advocate making the request to WRI. If enough people ask, they do try to spend the time to improve features. But if nobody asks, it probably won't get done.
Feb
17
comment Cut and paste data from a spreadsheet
Well, that is not part of the OP's question. She just wanted to copy the data, not make it look like it was a spreadsheet. Putting it in a grid makes it more difficult to manipulate.
Feb
17
comment Conditional Convolution
Also, your function f (the first one inside Convolve) is not defined correctly. You have a trailing [x], but the head is not a function.
Feb
17
revised Conditional Convolution
deleted 21 characters in body; edited tags
Feb
17
comment Conditional Convolution
If is not a mathematical function. Try something like HeavisideTheta instead. Also, what do you mean "the computer does not respond"? Do you mean that Mathematica crashes? (Also, please note how I formatted your post. Please don't use $\TeX$ markup in place of code blocks.)
Feb
16
comment Benchmarking Mathematica performance on the Raspberry Pi
A USB connector is not rated to supply 2A (even the specialized charging connectors are only rated for 1.5A), so this is probably where your voltage drop comes from. Perhaps it would operate better if a dedicated power supply was used. An additional decoupling capacitor may also be useful.
Feb
16
comment FindFit for simple a Sin[b x + c] gives FindFit::nrlnum mesage
Should work. I suggest you restart the kernel and try again. If no good, you may have some small complex values or some non-numeric contamination inside data.
Feb
16
comment How do I find my maximum precision on my computer?
$MaxExtraPrecision is not a fixed quantity. If you want it higher (or even infinite), you only have to ask.
Feb
14
comment How can I replace the Greek symbols in an expression with their plain text names?
Also, System`Private`CharacterNames[] lists all the named characters and FromCharacterCode@System`Private`NameCodeLookup@System`Private`CharacterNam­es[] gives a string of them (i.e., System`Private`NameCodeLookup is a bidirectional function). Extracting the Greek ones may be more difficult. (I also found that LetterQ recognises Greek letters, but contrary to its documentation, LetterCharacter does not.)
Feb
14
comment Double integral over normal pdf gives inconsistent answer
Switch Integrate to NIntegrate. It seems that the machine precision values in your expression make it impossible to get the correct answer symbolically when posed in this way.
Feb
14
comment How can I replace the Greek symbols in an expression with their plain text names?
System`Private`NameCodeLookup@ToCharacterCode["αβγδ"] -> {"Alpha", "Beta", "Gamma", "Delta"}
Feb
14
comment Performance boost for definite integration with symbolic limits
Incidentally, one can see that producing the conditional does not account for the whole time taken by giving the option GenerateConditions -> False. The integration takes about half as long, but is still much slower than if this were the only time-consuming operation.
Feb
14
comment Performance boost for definite integration with symbolic limits
Thank you for sharing your experience, but I have to say, I feel that this is not a question and your answer is not an answer. Definite integration is not as simple in general as this case might suggest, because the result can depend on the path taken in the complex plane in the presence of branch cuts. It is probably this branch cut handling that takes Mathematica the bulk of the time, although someone with more experience with Integrate could tell you for sure. Additionally, it would be better if you would specify what Maple is doing to evaluate the integral and what result it gives.
Feb
14
comment FindFit runs extremely slow for my Function,how do I optimize this?
NMinimize I think will use differential evolution by default, which (being a population-based method) is notoriously profligate with its use of objective function evaluations per iteration. That's why I specified Nelder-Mead in my comment above.
Feb
13
comment FindFit runs extremely slow for my Function,how do I optimize this?
Some comments: P should not have u as a parameter; your options for NIntegrate are malformed; IVsqData should be TestData. Apart from that, try Method -> {NMinimize, Method -> "NelderMead"} as a parameter for FindFit. It may not help that much, but the only constrained method FindMinimum offers is nonlinear interior point, which for some reason is very slow. NMinimize has a different approach to constrained minimization that could be faster. However, best of all would be to eliminate your constraints and modify the function so that unwanted values are made explicitly invalid.
Feb
13
comment Why is my rasterized graphic blank?
@Mr.Wizard version 10 cannot be installed on Windows 2003. On Windows 7, 10.0.1 does not exhibit the bug. I didn't install 10.0.2 yet.
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