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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?
Dec
19
comment Reduce function response to a single number
See this recent answer by Mark McClure. It gives some relevant tricks you could use.
Dec
18
comment Animate skips frames and hard to control speed.
Yes, the truth is that for one-parameter list of images I usually would suggest pre-computing all images and using ListAnimate, but you already ruled that out in the question. The reason I prefer this is that you will often want to display the animation more than once anyway, and then it would be increasingly inefficient to re-do the necessary computations every time, the more often you intend to display them.
Dec
17
comment Using If statement for more than two cases
In the Help browser, look up If and follow the links under "See Also".
Dec
17
comment Computing with matrix differential operators
Ah yes, that's because Plus inside Thread is not held unevaluated when its arguments have values that are known at the time of evaluation. To make it works for such cases it's probably best to avoid Plus - I'll edit the answer to deal with the example you gave.
Dec
7
comment How to solve time dependent Optical Bloch Equations for a three level system?
Can't say anything without seeing the equations, but first order of business has to be to eliminate all unnecessary parameters by suitable rescaling. But purely symbolic solutions are unlikely to be viable for high dimensions. I don't understand whether you're using numerical coefficients or not.
Dec
6
comment 3d phase portrait for a system of DEs
@SjoerdC.deVries Terminology always depends on the context of the field. What you mean is a phase-space portrait.
Dec
6
comment 3d phase portrait for a system of DEs
@SjoerdC.deVries Yes, it's standard terminology in differential equations.
Dec
6
comment 3d phase portrait for a system of DEs
@SjoerdC.deVries In the terminology of the linked package, phase plot just means a portrait of the flow in real space.
Dec
2
comment How to “undo” SetOptions (restore defaults)
Something like this was used here, although that was about Attributes, and not Options... (+1)
Dec
2
comment How to “undo” SetOptions (restore defaults)
possible duplicate of How to restore function attributes to default
Nov
26
comment Function to calculate finite difference
@user21 Great - thanks. That's a valuable resource, I think.
Nov
26
comment Function to calculate finite difference
To answer your question, check the documentation (not very easy to find online): tutorial/NDSolveMethodOfLines - explicit formulas are above the heading for FiniteDifferenceDerivative. Maybe this should be closed as "easily found in the documentation" - but it's not that easy to find, so I could also post an answer if needed (or even better: answer your own question).
Nov
25
comment What are the steps using boolean algebra for transforming one equation into another?
Ah, sorry but that's not possible with built-in functions. You can only do it in a single step: BooleanConvert[Ykmin] gives you Ydmin except in a different order.