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Aug
15
comment Finding average error of the data
@Mike a) that code doesn't work unless I know temp, b) is it too much to ask what doesn't work with LinearModelFit or the NonlinearModelFit example I gave?
Aug
15
comment Finding average error of the data
If, for example, dat = Table[{x, Sin[x] + RandomReal[{-.2, .2}]}, {x, 0, 10, .1}]; (because the code you gave needs a location and other parameters and I don't know, nor want to learn, how to set that) then eg mdl = NonlinearModelFit[dat, a*Sin[b*x] + c, {a, b, c}, x] finds a model and you can find for example the variance like so Variance[dat[[All, 2]] - mdl /@ dat[[All, 1]]].
Aug
15
comment Efficient Langevin Equation Solver
@chris I don't know to be honest. Why not write to him?
Aug
14
comment Test a wooden board's vibration mode
@Mr.Wizard OK, as you can see I did not vote for it to be closed. Maybe you're right.
Aug
14
comment Test a wooden board's vibration mode
@Mr.Wizard Also, it's not that unreasonable to expect that the answer to this could be modified to apply here. Does it? Does it not? Why not? We're not told.
Aug
14
comment Test a wooden board's vibration mode
@Mr.Wizard I'm not implying that anybody is getting pressured. All I am saying is that this is a question of precisely the same type as the one I posed, which presumably you'd not find good (as it is not well written, not necessarily valuable for future readers unless and not of reasonable scope, as it does not even attempt to express things in programming terms). That is, it does not satisfy 3 of the 4 criteria in the question you linked to.
Aug
14
comment Test a wooden board's vibration mode
@Mr.Wizard Would you also think that "please show me how to find the ground state of the 2d Kitaev model with Mathematica's linear algebra tools" is of reasonable scope? If not, why not? (in fact, mine is a much, much less technically involved question--unless we do include the spruce bit).
Aug
8
comment unlisting a nested list
do you mean that you literally have the symbol c and would like to end up with c1 and c2?
Aug
8
comment Removing some data and replacing them with new ones
In addition to what @RunnyKine said, here's what actually happened: you ask a question that seems to be answered by Differences. Then it turns out what you actually want is a filter to replace data if (roughly) the gradient is higher than some value by some interpolated value. But this is only clear from reading the comments. It would help in getting an answer if you included the info from the comments in the question (maybe with a short version of your data and some rough attempt to do what you want). Basically, imagine you don't know what the question is.
Aug
7
comment $SU(4)$ Structure constants in mathematica
So where did you get stuck?
Aug
7
answered How to sort my list?
Aug
7
answered How to integrate a function which is only known at discrete points
Aug
5
comment Matrix containing ellipse
Doesn't MorphologicalComponents[ Rasterize[Graphics[Disk[{0, 0}, {2, 1}]], ImageSize -> 800]] give a matrix?
Aug
4
comment How to make Eigensystem in version 10 produce the same results as version 9
@xslittlegrass right, I know the closed form solution from the papers I cited (that's where I first saw them, but I am not sure if they first appeared elsewhere). If you're interested in general potentials and/or time dependent solutions then you indeed have to do it this way (numerically). As to how I knew it, I guess it's like asking "wow how did you know this is the Schrodinger equation?" isn't it? Now, if you had an interacting Hamiltonian and I spotted the potential, that would have indeed been noteworthy :)
Aug
4
comment How to make Eigensystem in version 10 produce the same results as version 9
Actually, your Hamiltonian is literally that of a SHO on a 1d lattice (plus noise). You can find analytical solutions to this here or here, although I'm not sure how useful they are to you.
Aug
4
comment How to make Eigensystem in version 10 produce the same results as version 9
@Jens I think here it really is due to degeneracies. It would have been useful to have a canonical question and answer to this somewhere.
Aug
4
comment How to make Eigensystem in version 10 produce the same results as version 9
You Hamiltonian has degenerate eigenvalues, see here. I am guessing this is a single particle in a harmonic oscillator potential (ListPlot[Diagonal[Chop@Hmtx]]), in which case the degeneracy is physically due to the reflection symmetry of the potential. If you plot the absolute value of the eigenvectors (the density) you'll see what is going on and why hybridisation is so weak.
Aug
3
comment Problem setting up C compiler on a Mac
@TedErsek You can most certainly write C programs for OSX (or any other language for which you have a compiler). XCode is an IDE, which is meant to help with writing code. It's focussed on objective C and C, but supports other languages. Now, you seem to have clang installed in the usual place, so there is some misconfiguration in mma itself. Does Compile[{{z, _Real, 1}}, Sin[z], CompilationTarget -> "C"] also return $Failed?
Jul
28
comment Sum with Levi-Civita
@Dave84 since you have explicit values for the $a,b,c$ you can use TensorProduct
Jul
28
comment Sum with Levi-Civita
It looks like LeviCivitaTensor, not LeviCivita. Also the code you give has syntax errors, and even if it didn't it doesn't work because a and so on aren't defined and when you try to retrieve their elements, you get an error. Not to put too fine a point on it, but you need to look at the docs.