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Oct
20
answered Why doesn't FullSimplify simplify expressions with DiracDelta?
Oct
20
comment Superscript prime symbol
Very closely related: How to Clear variables with apostrophe? There, I suggest using a different unicode glyph that looks better.
Oct
20
reviewed Close How to regress negative log?
Oct
20
reviewed Close Non-aggregated solution for NonlinearModelFit
Oct
20
comment Derivative of an expression containing a symbolic sum
Yes, that's right.
Oct
19
comment Derivative of an expression containing a symbolic sum
@StripesPlaid Indeed, the last simplification works in Mathematica version 10.0.1, but not in version 8. I'm guessing you're using an older version. The TagSetDelayed rule for $\beta$ only gets applied in the 10.0.1 version after the derivative has been done under the sum. Then what the rule says is that whenever $\beta$ appears as the summation index without any additional range specification, and there is a Kronecker delta involving $\beta$, you're supposed to reduce the sum to the rest multiplying the delta.
Oct
19
answered Derivative of an expression containing a symbolic sum
Oct
19
comment Derivative of an expression containing a symbolic sum
This is probably a duplicate of how to differentiate formally. You only have to get rid of the Subscripts as variable names because they bury the meaning of the actual labels $\alpha$ and $\beta$ too deeply. Replace Subscript[lambda][alpha] by lambda[alpha] etc.
Oct
18
comment How to tell Eigensystem the type of the elements comprising a matrix I would like to diagonalize
@lagoa But that time is negligible compared to the computation of the eigensystem.
Oct
18
reviewed Close a complicated Sum
Oct
18
reviewed Close Concisely returning a position in an array with an index variable
Oct
18
comment How to tell Eigensystem the type of the elements comprising a matrix I would like to diagonalize
It's not clear to me what you mean. Are you trying to find a symbolic solution first by using assumptions, or do you want to define a function that takes a numerical argument and returns the Eigensystem, or is M already numerical but written in terms of arbitrary-precision numbers, or something else? Please include a minimum example to clarify what you're trying to do.
Oct
18
reviewed No Action Needed Equivalent of RadialOutside for Graph VertexLabels
Oct
18
reviewed Close Numerical solution to two non-linear coupled differential equations
Oct
16
comment Simplifying general solutions of differential equations (driven harmonic oscillator)
I really think the _C approach is unbeatable, so this should be the accepted answer. So I'll just leave it up to you if you want to mention Apart.
Oct
16
comment Simplifying general solutions of differential equations (driven harmonic oscillator)
The result of collecting over m is smaller, but not very systematic because m is a variable that could easily be eliminated from the entire problem. A more systematic way of getting that same result seems to be Simplify /@ Apart@Simplify[sol]. Here I use the fact that Map can also work on expressions that don't have head List - which is also something the OP could have used to avoid converting to List initially. But I think what the physicist expects is really the result of collecting over _C...
Oct
15
comment Simplifying general solutions of differential equations (driven harmonic oscillator)
This is a nice and general method for linear differential equations because the C[i] will always be multiplicative in front of the homogeneous solutions, so collecting them is the natural choice (+1).
Oct
14
comment 2D Fourier transform of a few (4) disjoint discs on a plane
@DumpsterDoofus I see, that's an interesting effect. I was using version 8 so I couldn't see that directly at the time.
Oct
14
comment 2D Fourier transform of a few (4) disjoint discs on a plane
@DumpsterDoofus (+1) In case anyone wants to reproduce the plot in a Mathematica version that doesn't have TensorProduct yet, it's also possible to just do the monochrome image first and then wrap it in Colorize[%, ColorFunction -> (Blend[{Black, RGBColor[1.0, 0.3, 0.1]}, #] &)].
Oct
13
comment How can I create a plot like this in mathematica?
There's also BoxWhiskerChart