38,127 reputation
155151
bio website uoregon.edu/~noeckel
location
age
visits member for 2 years, 2 months
seen 21 mins ago

Apr
1
comment What is the mathematical meaning behind D[f]?
@MichaelE2 Right. I wonder if there's also a continuation to negative derivatives like in Derivative[-1], which is indeed the integral. Maybe f[x[D]]?
Apr
1
comment Shrinking the size of exported 2D density, vector field, and streamline plots
Try the function rasterTrick from my answer here.
Apr
1
comment What is the mathematical meaning behind D[f]?
@rm-rf You may well be right - but I thought it's OK to postulate "innocent until proven guilty"...
Apr
1
comment How does Mathematica understand branchcuts of the complex logarithm?
@user6818 No, that's not quite right. The choice of contour in complex integration is actually the way in which you, the user, define the quantity you want Mathematica to compute. This is becoming more of a math discussion, so I don't think it's fruitful to continue in the context of the original question.
Mar
31
comment Writing a simple application: interactive quiz for multiplication table practice
You may also want to look at the answers to this: Automatically check student answers in tests. In my answer there, I focused on making free-form input "secure" while still allowing symbolic input. This isn't what you need, but it's related. In my answer, the Enter key is used only to submit answers. The Tab key is used to go to the next answer.
Mar
30
comment How does Mathematica understand branchcuts of the complex logarithm?
Mathematica cannot know along which contour you want to integrate. You have to tell it. Your question is about Mathematica's understanding of branch cuts of Log, and I explained that they arise from the phase angle convention. But Log is only one of infinitely many choices for the inverse of the Exp function, and all others can be generated by fixing a different $\phi$ interval for the phase angles. The quantity $\sigma$ is the lower bound of that interval of length $2\pi$, as seen in the definition of log above. It's pretty standard textbook stuff, but looks nice in your example.
Mar
30
comment Can Mathematica find the discriminant formula?
The command Discriminant (see the documentation) does what you want. Of course you can also re-invent that function yourself. Do want exactly the same functionality?
Mar
30
comment How does Mathematica understand branchcuts of the complex logarithm?
@user6818 I added more information to my answer, although I had to guess what it is that you really want to know.
Mar
29
comment How to speed up this TDSE code?
@LeonidShifrin It looks like you can get the same speed by replacing your SparseArray construct with the simpler Vmtx=DiagonalMatrix[SparseArray[(V[t]/@xls)]]
Mar
29
comment How to speed up this TDSE code?
@xslittlegrass To make it work on version <9, you could replace the definition of Ct0 by this: Ct0 = Table[Exp[-x^2], {x, -10, 10, 20/399}] // N; (the construct where Array fills slots in a range {a,b} given by the third argument doesn't exist in earlier versions).
Mar
26
comment How does Mathematica understand branchcuts of the complex logarithm?
I may have time to get back to this later, but in the meantime you may want to look at this post: How to calculate contour integrals with Mathematica
Mar
26
comment How to create .ico file in Mathematica?
@Problemaniac It's not necessary, but I threw it in as a guess because I don't know for sure why the OP is having trouble. Maybe the answer boils down to: upgrade to version 9.0.1.
Mar
26
comment Asymptotic expansion
You can get that to work if you use a different expansion variable, e.g.: Series[Tanh[Log[z]], {z, Infinity, 2}] but not with the variable M, as explained in the link I posted. But that's basically a math question, and Mathematica is handling it correctly, I believe.
Mar
26
comment Asymptotic expansion
That case is again very different. You're asking for an asymptotic expansion of Tanh in its argument, which doesn't exist. I'm afraid there isn't anything more general I can say, there are too many possibilities. Maybe the best advice is to boil your expression down as far as you can by eliminating unnecessary variables that can be absorbed or scaled out.
Mar
26
comment How to create .ico file in Mathematica?
What version of Mathematica are you on, and what OS? I'm guessing version 8, right?
Mar
25
comment FlipView can't handle CurrentValue[“MouseOver”]. Kernel crash
The EventHandler workaround from the linked answer doesn't really work here. I accidentally got it to "work" with the wrong syntax: FlipView[{EventHandler[Framed[...],Framed[...], {"MouseUp",2}:>Null]}] which strangely produced neither an error message nor a crash. But wrapping Framed individually doesn't prevent the crash.
Mar
25
comment Avoid crash in recursive Dynamic
Absolutely, for your application this isn't going to work.
Mar
25
comment Avoid crash in recursive Dynamic
@Kuba, yes, I think this was fixed in the meantime - I don't see the crash on 9.0.1 anymore. But in your question here, the fix seems to work.
Mar
25
comment FlipView can't handle CurrentValue[“MouseOver”]. Kernel crash
Perhaps related: Avoid crash in recursive Dynamic. The fix there does seem to work here if it wraps Framed.
Mar
25
comment Solving Heat equation
You could solve this numerically with NDSolve, but the boundary conditions are inconsistent with the initial condition at t=0. If you replace them by u[10,t] == u[10,t] (periodic boundary conditions), the numerical approach will work after correcting the syntax.