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Feb
4
awarded  Nice Answer
Feb
1
comment Why Mathematica chooses bracket for function arguments over parenthesis?
"If function arguments are denotes as f(x), then array[i] could be used as array index.(c.f. Mathematica uses [[i]] here.)" — is (f + g)(x + y) parenthesizing and multiplying two terms or is it a function call (like (f + g)[x + y] in the current syntax)?
Jan
31
awarded  Nice Answer
Jan
29
awarded  Good Answer
Jan
17
awarded  Yearling
Jan
15
awarded  Notable Question
Jan
10
comment Invert Colors Stylesheet White on Black
You can also look at this answer of mine for some hints on what to change and where, and maybe also look through Mike Honeychurch's answers in notebooks/stylesheets tags. Also look through the Default.nb and Core.nb stylesheets for the base styles that you can modify. It's a lot of boring work.
Jan
10
comment Invert Colors Stylesheet White on Black
If the older one hasn't been answered because it is difficult, then yours won't be either. If the older one wasn't answered because it wasn't interesting, then yours probably won't be either... questions on stylesheets are fickle and often it's the case that the answer is "straightforward" but no one wants to do the grunt work. In any case, you might try sweetening the deal with a bounty on the original and see if someone will take the bait :)
Jan
9
revised How well does my function fit data?
rolled back to a previous revision
Jan
7
comment Is there an equivalent of “pmtm” of MATLAB?
We can't help with C++/C# conversion either. You can look at the source code by typing edit pmtm. That should give you hints to proceed with your translation attempts.
Jan
7
comment Is there an equivalent of “pmtm” of MATLAB?
If you use MATLink, then it is as simple as pmtm = MFunction["pmtm", "OutputArguments" -> 2] after you initialize the package. You'd call it as {p, f} = pmtm[data, tapers, n, fs].
Jan
7
comment Apply ColorFunction to an Image
@DJJ I think this is what you're looking for: mathematica.stackexchange.com/a/67217/5 The question might even be a duplicate.
Jan
7
comment InterpolatingFunction used to work with mathematic 7 but not working with mathematica 10
See here: mathematica.stackexchange.com/a/28341/5
Jan
4
comment Speed up replacement using Rule Dispatch Associtation
I'm not surprised. It's not unconceivable that Transpose[DD1].DD1 is more complex (in terms of leaf count and computations involved) than just DD1. What I said in my previous two comments was that you should go back to the drawing board and see if you can use mathematics to simplify the problem before throwing it to Mathematica. Since we don't know the origins of your problem or how you arrive at kappa, we cannot help you there (nor is this necessarily the site for that).
Jan
4
comment Speed up replacement using Rule Dispatch Associtation
Note that the rank of your matrix $X$ is bounded by the number of columns which is much less than the number of rows. Does your formulation permit an easy calculation of $X^\top X$ which is only $30\times 30$ (or $100\times 100$ in the bigger one)? If so, then you can try and compute the rank of that, as it should be the same as the rank of $X$. Assuming that all elements of $X\in \mathbb{R}^{n\times m}, n \gg m$ take roughly the same time to compute and the time taken to compute an element of $X$ is the same as $X^\top X$, then you've gone from having to compute $O(n m)$ elements to $O(m^2)$.
Jan
4
comment Speed up replacement using Rule Dispatch Associtation
I think this is a dead-end in terms of having a general answer. Suggestions and tricks that might help speed this up will likely depend on how the kappa expression is obtained, about which you don't say anything. We're effectively being asked to analyze and optimize a blackbox expression. You should perhaps consider stepping away from Mathematica for a bit and turning to mathematics to try and simplify the problem.
Jan
4
comment Rapid density estimation and rendering of decision regions
One thing you could do when using Manipulate with compute-intensive demonstrations is to use ControlActive with the variable being changed. That way, the evaluation doesn't try to kick in midway during the slider adjustment and the plot is redrawn only when the slider is released. It doesn't address the inherent slowness of the computation, but does give a semblance of interactivity and overall less choppiness.
Jan
3
comment Can a System symbol spontaneously leak into a Global namespace?
To give an example, see this discussion between me, Leonid and Rojo. In the end, the mistake was mine — I hadn't fully isolated all my private symbols and a few of them happened to get exposed only in some very specific order of internal function calls. The point I'm trying to make is that this bug (albeit minor) crept into a smallish but non-trivial package that had extensive unit-tests and was identified only a year later. It is very likely that there are hundreds if not thousands of these in the Mathematica code base.
Jan
3
comment Can a System symbol spontaneously leak into a Global namespace?
Re: A – I have seen behavior like this, yes. Mathematica is a complex piece of software and some hard to detect bugs like this can often come up even in internal code. Re: B — As you say, it's hard to produce a minimal example for bugs like this (understandable), but it also makes it hard for us to try and troubleshoot. The question then becomes: Is this affecting your work? If so, how? That would give us a concrete path to proceed. If not, then I would suggest ignoring it or silencing it.
Dec
29
reviewed Leave Open RegionPlot fails when given function with internally redefined variables