51,744 reputation
281206
bio website uoregon.edu/~noeckel
location
age
visits member for 3 years, 2 months
seen 31 mins ago

Mar
19
comment Very slow mathematica finite differences
@shrx It's unnecessary here, but sometimes it can be useful because without it, While could remain unevaluated if the condition doesn't evaluate to True or False. This is among the "cosmetic changes" I mentioned.
Mar
19
comment Very slow mathematica finite differences
@xzczd I forgot to add that - thanks! Of course, in reality FORTRAN is unbeatable for speed, but at least Compile gets reasonable speed.
Mar
19
comment Very slow mathematica finite differences
Can't look at the details, but one thing jumps out in the first line: fGetNu gets re-compiled every single time it's invoked because it's defined with SetDelayed. Probably if you state the problem you want to solve, someone can come up with a better method using built-in functionality.
Mar
18
comment Simultaneously fitting two data sets to two functions is too slow
Your code doesn't run. It has errors in how the functions are defined. Without some example data, it's not possible to execute the fit.
Mar
18
comment How do I find local minimums in data?
Yes: FindPeaks[-data] would do that.
Mar
18
comment What if do NOT want Mathematica to normalize eigenvectors with Eigenvectors[N[matrix]]?
I think the proper way to handle your kind of issue is to rescale the matrix before calculating its eigenvalues, to make it more well-behaved. But in the absence of an actual example, I can't think of a good way to write a useful answer.
Mar
18
comment Plotting: Magnetic field lines
You could do an interpolation of your data and then apply my answer posted here. But how to do the interpolation depends on the grid geometry and data density.
Mar
18
comment how can I bold the outline of conic section as the plane intercepts the cone?
@SjoerdC.deVries I'd suggest the OP clarify the question so as to not waste time with misinterpretations...
Mar
18
comment Problem using Rotation in Show
You can't combine 2D and 3D graphics within a single Show. It's either one or the other, so you have to apply the conversion to 2D to both objects.
Mar
18
comment how can I bold the outline of conic section as the plane intercepts the cone?
possible duplicate of About Slicing through Graphics3D
Mar
18
comment Font style in Mathematica matching \mathcal and \mathbf in Miktex
The boldface part is trivial: just make the input boldface and (if desired) toggle italic. The keyboard shortcuts for this are the same as in most other application but that depends on your operating system. Maybe it's best to refer you to this link: Mathematical Typesetting
Mar
18
comment Phase Portraits
Have you tried GraphicsGrid?
Mar
18
comment Time Zone Conversion
It's elementary. Just stick with terrestrial time.
Mar
17
comment Convolve does not get the correct answer
Thanks for the analysis in edit #3. I already upvoted you before giving my own answer... couldn't believe that I actually stumbled on a bug there.
Mar
16
comment Schroedinger eigenvalue problem in two dimensions (Harmonic Oscillator)
It's relatively simple: if you have chosen a length unit by specifying a in the code, you need to bring the kinetic-energy term into the form $-(1/2) d^2/dx^2$. To do this, you have to choose the unit of energy appropriately.
Mar
16
comment Convolve does not get the correct answer
@DanielLichtblau Thanks for taking a look. It's sneaky because the c in Erfc is easy to overlook, and with Erf it would almost be right (up to a sign).
Mar
16
comment Convolve does not get the correct answer
@DanielLichtblau We just noticed that this really is a bug in Convolve. My answer below evaluates to the wrong result in versions 8 and 10.9.5
Mar
16
comment Convolve does not get the correct answer
Your answer is probably the only one that works because Convolve in my answer is buggy. In that case, I think the question is actually a duplicate of Convolving/integrating problems.
Mar
16
comment Convolve does not get the correct answer
Right, this seems to be a huge bug in Convolve.
Mar
16
comment Transforming expressions in terms of Csc and Sec to expressions in terms of Sin and Cos
Although the goal here is a little different, I think the main issue is the same as in Mathematica Sec and Csc, and there probably isn't a better solution - I would love to be wrong, though.