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2d
comment Bug in associated Legendre Polynomials?
Actually, I think there is something wrong here. The answer is correct if taken by itself, but it is inconsistent with the definition of SphericalHarmonicY because there you do get 0 for {l,m} = {1,-1}.
Jan
19
comment Embed 3D objects from Mathematica, in a pdf
Looks like u3d export is really hard to come by, except for jReality. You might try that...
Jan
19
comment Embed 3D objects from Mathematica, in a pdf
Oh, you can also google latex package media9. I just mention texdoc because that's the standard way to get documentation about TeX packages. That package I refer to allows you embed 3D objects in PDF. But it's a bunch of steps that need to be done external to Mathematica. In fact, the main obstacle is that you need u3d format, and Mathematica doesn't export that directly.
Jan
19
comment Embed 3D objects from Mathematica, in a pdf
Just do texdoc media9 in a terminal and read the section on 3D. I don't think this is a Mathematica question. Export of 3D formats is supported, but embedding them in PDF (a non-3D format) for the specific purpose of displaying in Adobe Reader appears to be beyond the scope here.
Jan
19
comment Incorrect evaluation of integral involving a DiracDelta, whose argument has infinitely many zeros
I've reported this as a bug (CASE:2323185).
Jan
18
comment Incorrect evaluation of integral involving a DiracDelta, whose argument has infinitely many zeros
(+1) Interestingly, the result looks correct if one does it with a polynomial instead of Sin[x], so the existence of branches of the inverse is not per se a deal-breaker.
Jan
18
comment Incorrect evaluation of integral involving a DiracDelta, whose argument has infinitely many zeros
This seems to be a bug. As you correctly point out, there are infinitely many zeros in the argument of the delta function, and they must be accounted for in a sum. There is no justification for omitting that sum, and it would give you an infinite series.
Jan
17
comment Least effort to handle a point source inside the domain of PDE(s)
I think you're right about the continuous limit being ill-defined, and that's why I modified the problem to put the driving in as a source term of finite size. The question still makes sense if we consider the grid as a given fixed structure, but this means NDSolve by itself doesn't seem to be the right tool here.
Jan
16
comment Least effort to handle a point source inside the domain of PDE(s)
In this answer, I just used a narrow Gaussian instead of a point. Maybe that's good enough...? After all, it's all discretized anyway, so points are never points.
Jan
13
comment Trying to model Heat flow trough different materials with NDsolve
@Laurent In order to get a jump in the derivative, one would have to specify an interface condition that is clearly not present in the original question. With the information in the question (which is not a steady-state problem and contains no conditions on the derivative at the interface), I think we can't get what you're expecting.
Jan
11
comment Vectorize pixel SphericalPlot
The code isn't self-contained, so it doesn't produce an image. But how about replacing Antialiasing -> True with Magnification -> 2 in the Style command?
Jan
10
comment Vectorize pixel SphericalPlot
You could try the function rasterTrick from my answer here. If that doesn't work, please explain the issue in more detail with some sample code.
Jan
10
comment Creating formulas for the Moodle CMS question bank
One quick thought: the output should be a String so you can copy it into a text field of the CMS. Also: maybe it's easier if you choose your variable names according to some pattern, e.g., moodle[a], moodle[b], etc.
Dec
25
comment Alternatives to FiniteElement as Spatial Discretization Method for NDSolve
For some more examples of how to use functionality that existed in previous versions, you may also want to look at FiniteDifferenceDerivative which I used in my answer to Finding the eigenfunctions of one and two dimensional Harmonic Oscillator and the previous post linked therein. Since much of the necessary functionality was missing, I ended up hand-rolling things like the relaxation method, e.g., here: Poisson solver using Mathematica
Dec
23
comment Computing the fundamental matrix and its monodromy matrix
This seems to be not only unrelated to the question but also unrelated to Mathematica.
Dec
22
comment version 5 & OS X 10.9
@Szabolcs I just checked, and the executable for Mathematica 5.2 is a Universal Binary, not restricted to PowerPC. This doesn't mean I'd encourage using that old version on 10.9, but it means it could work in principle.
Dec
21
comment version 5 & OS X 10.9
I can run Mathematica 5.2 on an Intel Xeon Mac with OS X 10.6.8, but even if you do manage to run it on 10.9 there will be real usability issues. See e.g. this link.
Dec
20
comment Can I define an axiomatic (Boolean algebra) system and prove theorems using Mathematica?
Also, you could do something like this: Simplify[Equivalent[Not[Or[a, b]], And[Not[a], Not[b]]]].
Dec
20
comment Buying a new computer (specifically for Mathematica)
GPU may be important especially if you plan to use CUDA or OpenCL. But it really is a very broad question which I don't believe has a unique answer.
Dec
20
comment How to check if Integrate solved the integral?
Why not just check Head[r]===Integrate?