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Jan
10
comment Polar Decomposition
from tutorial/LinearAlgebra/MatrixManipulation.html, it says "Compute the polar decomposition of a matrix:" {u, w, v} = SingularValueDecomposition[{{1, 1}, {1, I}}]; {u.ConjugateTranspose[v], v.w.ConjugateTranspose[v]} // RootReduce
Dec
31
comment Initial value problem with Laplace transform
Laplace transform works from t=0 on. You have input for negative time. Have you tried using DSolve? why do you have to use Laplace transform for this?
Dec
31
comment How to get short definition of all built in Mathematica Functions?
I'd use what Bill showed, but another option is Information[Evaluate[ToExpression[functionslist[[1]]]]]
Dec
31
comment Format Exp[] in output
The FullForm of all of these is the same, which is Power[E,argument]. So the differences are in screen presentation. To be able to do what you want, my guess is one must go to lower level and use MakeBoxes and such to force the screen display to Exp[..], which is out of my level of skill. May be someone will be able to do this.
Dec
31
comment Format Exp[] in output
InputForm[expr] uses E^..., may be you can try InputForm? For example, screen shot: !Mathematica graphics
Dec
30
comment Derivatives of overscript variables
Try the notation package and the Symbolize command. (but what you are trying to do is very confusing. Why not use normal symbols?)
Dec
27
comment Random real numbers that sum up to specific value
What is wrong with: n = 5; numbers = RandomReal[{0, 1}, 5]; numbers = numbers/Total[numbers] which gives {0.269286, 0.313348, 0.0546711, 0.191817, 0.170879} which adds to 1
Dec
20
comment Different results of a definite integral $\int_0^{\cosh ^{-1}(a)} \frac{1}{\sqrt{a^2 \text{sech}^2(x)-1}}\, dx$
@JunhoLee I also just verified it with Rubi, it also gives -Pi/2 or 3 Pi/2 : !Mathematica graphics so I think the symbolic result is correct. May be there is problem with numerical integration.
Dec
20
comment Different results of a definite integral $\int_0^{\cosh ^{-1}(a)} \frac{1}{\sqrt{a^2 \text{sech}^2(x)-1}}\, dx$
@JunhoLee Well, may be, but looking at: r = Integrate[1/Sqrt[-1 + 2^2*Sech[x]^2], x]; Limit[r, x -> ArcCosh[2]] - Limit[r, x -> 0]; N[%] gives -Pi/2 and -Pi/2 is actually the same as 3 Pi/2 However, NIntegrate[1/Sqrt[-1 + 2^2*Sech[x]^2], {x, 0, ArcCosh[2]}] gives Pi/2. So I am not sure. May be someone knows.
Dec
20
comment Can I define an axiomatic (Boolean algebra) system and prove theorems using Mathematica?
Wolfram is working on adding pure math to Mathematica, here is his blog on this computational-knowledge-and-the-future-of-pure-mathematics/ the idea is that one should be able to proof things and do more pure math using Mathematica. Proofs can be generated or checked. But this is for future versions.
Dec
20
comment Buying a new computer (specifically for Mathematica)
get a mac for Mathematica. many at WRI use mac's not PC's. I think due to origin of how Mathematica was created, it is apple first, windows second, and then Linux 5th.
Dec
20
comment How to check if Integrate solved the integral?
@Jens sure. This sounds like a smart way to go about it. I did not think about it.
Dec
13
comment about the design of Part related to Association
I found more documentation on part with association. it is all here reference.wolfram.com/language/ref/Part.html about half way down the page. many examples.
Dec
13
comment about the design of Part related to Association
I think I figured it. To obtain the whole part, i.e. (key->value), one must use [[n;;n]] syntax or [[n;;]]. But if you use [[n]] this will only give the value at part n. The reason why [[n;;m]] work for both key,values at both n through m parts, is because of the ;; usage. So to pull both key+value, use ;;, else it will default to only the value at that part.
Dec
13
comment about the design of Part related to Association
I agree. It is not consistent. May be it is a bug?
Dec
13
comment Plot with Mathematica
nice. but no control buttons :)
Dec
12
comment AbsoluteOptions prints error messages in V10
@gwr I see. I was only using the example provided. For the example given, it did not give an error. There is a new post today on AbsoluteOptions problems also. mathematica.stackexchange.com/questions/68937/… so it seems there is more issue still with this. May be you can post your example as separate question? This will make it easier to track it on its own?
Dec
12
comment Fourier and InverseFourier precision
Chop[x1 - Abs[x1]] gives {0, 0, 0, -1.5136, -1.91785, -0.558831, 0, 0, 0, -1.08804, -1.99998, -1.07315, 0, 0, 0, -0.575807, -1.92279, -1.50197, 0, 0}
Dec
12
comment Solve a differential equation with an integral inside?
@NimblePawn added Laplace method. Not sure why -Sin[t] shows up in the ODE method vs. +Sin[t] in the Laplace now. But these are two methods I know about. The correct answer with zero IC should be the ODE based one. with -sin.
Dec
11
comment TableView displays negative numbers incorrectly
same problem in 10.0.2