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visits member for 2 years, 3 months
seen Jun 24 '13 at 0:02

No, his mind is not for rent
to any god or government.
Always hopeful, yet discontent.
He knows changes aren't permanent,
but change is.

— Rush, Tom Sawyer


Taking an externally-imposed and much-needed break from SE activities.

E-mail (flipped ROT13): zqd˙ʎʌuzʇ@ʇɐʌǝɥʇʌssqɹǝɥɟuɹʎɔ
Any code I've posted here I place under the WTFPL.


Jun
23
revised How to choose three points on the circle so that the triangle is not a right triangle?
edited tags
Jun
23
revised Malliavin Derivative with Mathematica is it possible?
edited tags
Jun
23
comment Numerical Integration with InverseErfc
This is an answer, but apparently not for this question.
Jun
23
revised Numerical Integration with InverseErfc
edited tags
Jun
22
revised I can't understand FindShortest Tour
edited tags; edited tags
Jun
22
comment Line perpendicular to a tangent line to a parabola behaves unexpectedly
Of course it will stretch quite a bit; your setting PlotRange -> {0, 100} is hella huge. The thing is, with the default AspectRatio setting, you just won't see lines that are supposed to be perpendicular as actually perpendicular, and the Automatic setting fixes that. See Jens's answer as well.
Jun
22
comment Line perpendicular to a tangent line to a parabola behaves unexpectedly
Add AspectRatio -> Automatic and report back.
Jun
22
comment Trace of FullSimplify
"if it is possible for Mathematica to show the steps" - not in this case, I believe.
Jun
22
comment Trace of FullSimplify
In general, the simplification methods internally used by Mathematica do not necessarily correspond to how one might simplify by hand; remember that a method that is simple for computers to do is not necessarily simple for humans, and vice-versa.
Jun
22
comment How to maximize a function over a rotation matrix?
I don't have Mathematica on me at the moment, but you might try {Array[K, {3, 3}], {p, q, r}, a, b} /. Last[NMinimize[Flatten[{Total[MapThread[SquaredEuclideanDistance, {f[#, Array[K, {3, 3}], {p, q, r}, a, b] & /@ x, y}]], Thread /@ Thread[Transpose[Array[K, {3, 3}]].Array[K, {3, 3}] == IdentityMatrix[3]], Det[Array[K, {3, 3}]] == 1, a > 0, b > 0}], Flatten[{Array[K, {3, 3}], {p, q, r}, a, b}]]]...
Jun
22
comment How to maximize a function over a rotation matrix?
...and some example points would be, y'know, cool too...
Jun
22
comment How to maximize a function over a rotation matrix?
Some more definiteness would be appreciated; in particular, what would your $f$ typically look like?
Jun
22
comment Change of coordinates for an InterpolatingFunction
I'm not sure; after all, this is undocumented functionality...
Jun
22
comment How to maximize a function over a rotation matrix?
In that case, you really should edit your question to talk about your actual problem, and maybe include sample data and expected results...
Jun
22
comment How to maximize a function over a rotation matrix?
You will want to look up FindGeometricTransform[]; it will be able to find the best rigid transformation between your two sets of points.
Jun
22
comment Have the Random functions changed?
No problem; I couldn't contribute much otherwise since I'm not using a machine with Mathematica at the moment...
Jun
22
revised Have the Random functions changed?
added 933 characters in body
Jun
22
comment Have the Random functions changed?
Actually, digging deeper into old docs, it would seem that the legacy method in fact uses the rule 30 cellular automaton in the integer case. This is borne out by the fact that "Legacy" and "Rule30CA" give identical results for RandomInteger[]. In short, version 8 uses "ExtendedCA" as the default, while version 9 uses "Rule30CA" by default, for both random integers and reals. Now we wait for somebody from WRI to explain this switch...
Jun
22
comment Simplify $\cos(n \pi)$ and $\sin(n \pi)$ when n is an integer
I'm not quite sure why one works and the other doesn't, even though they are ostensibly equivalent; the reason I left a comment is because I am not at a machine with Mathematica. Might I suggest writing your own answer to your own question instead?
Jun
22
comment Simplify $\cos(n \pi)$ and $\sin(n \pi)$ when n is an integer
Did you already try Assuming[Element[n, Integers], 2/Pi Integrate[Cosh[a x] Cos[n x], {x, 0, Pi}]]?