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Feb
3
comment Bug? Kernel Crash on SparseArray access
Confirmed in v8.0.4 and v9.0.1, vista 32bit.
Jan
31
comment System of differential equations
possible duplicate of Why my differential equations become True?
Jan
31
comment NIntegrate and Integrate of a Spherical Bessel function
You misread OP's expression again, it should be BesselJ[15/2, BesselJZero[15/2, 1] r]^2 r
Jan
29
comment NIntegrate and Integrate of a Spherical Bessel function
Well, I'm afraid this isn't the integrand OP struggling with…
Jan
26
comment Brevity of denoting Conjugate[]
TraditionalForm?
Jan
24
comment Boundary sphere partial differential equation
Er… so what's your boundary condition of θ, in traditional math notation? BTW I think it'll be better if you mention some background information of your PDE.
Jan
22
comment Differential equation with a Heavisidetheta function running for ever
You've made a small mistake. y[L] == 0 and y''[L] == 0 can't be used in the first half as boundarys. If you Show the numeric and symbolic result, you'll see they're different :)
Jan
19
comment Least effort to handle a point source inside the domain of PDE(s)
Interesting……Well, does this mean if we stick a infinite thin rod on an unbroken membrane, the membrane won't have any displacement except on the stuck point?
Jan
17
comment VectorScale Explanation
I tried to improve the format and fix possible typo, if I misunderstood some part of your question, feel free to roll back… Well, with all due respect, as a member for 2 years, you should have format this question better.
Jan
17
comment One less arrow vector than asked for
Desired result in v8.0.4 and v9.0.1. I think it's reasonable to consider it as a bug.
Jan
17
comment Least effort to handle a point source inside the domain of PDE(s)
@Jens Yeah, that sounds reasonable. Maybe you can consider giving an answer?
Jan
16
comment The default ColorFunction of DensityPlot before v10?
@BrettChampion Oh……I see. You can make this into an answer, anyway it's not that obvious, I think.
Jan
10
comment Why is my data 10 times slower than random data when doing matrix multiplication
@xslittlegrass 15.954589770191005 == MachinePrecision does return True, but when using as precision, they're different, the latter represents machine precision, while the former represents arbitrary precision, they lead to 2 different algorithm… well, it's a little hard for me to explain in my own words, but there're many related posts in this site, for example this one.
Jan
9
comment Workarounds for a possible bug in the linearity of FourierTransform
Seems this hasn't been done yet. Hello, welcome to Mathematica.SE! I suggest the following: 1) As you receive help, try to give it too, by answering questions in your area of expertise. 2) Read the faq! 3) When you see good questions and answers, vote them up by clicking the gray triangles, because the credibility of the system is based on the reputation gained by users sharing their knowledge. Also, please remember to accept the answer, if any, that solves your problem, by clicking the checkmark sign!
Jan
9
comment Computation time depends on the matrix elements!
A better check is {Or @@ PackedArrayQ /@ matrix, And @@ PackedArrayQ /@ matrix2} :)
Jan
9
comment Can I force Mathematica to use machine precision?
The only thing I can think of at the moment is Compile, is it of interest?
Jan
9
comment Inverse Fourier Transform - wolfram alpha vs Mathematica 9.0
It's simply because the InverseFourierTransform of your expression doesn't exist. Try InverseFourierTransform[Exp[ -b v^2], v, w, Assumptions -> #] & /@ {b > 0, b < 0}
Jan
9
comment Possible bug with FourierTransform linearity
Just wrote a "shell" for FourierTransform here, which (I think) is a little more stable than the Distribute approach.
Jan
8
comment Integration of a high oscillatory function
@yashar Just search MachinePrecision and WorkingPrecision, and you'll see lots of posts about how and why precision dramatically influence the result. I used to collect just 4 of them here.
Jan
7
comment Integration of a high oscillatory function
@yashar Yeah, that's expected result. 1000 is a number with infinity precision, while 1000.0 is a number with MachinePrecison. There're many posts about this issue in this site, have a search :)