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# 1,286 Comments

 Apr 20 comment Problems with numerical solution of differential equation if all these f1[z], f2[z],  etc.. are meant to be functions (and they look like it) then you missing _ there after the z Apr 6 comment StringPattern to remove markers around text Thanks. It is the Shortest which I did not know to use. Apr 3 comment SystemException[“MemoryAllocationFailure”] Uncaught SystemException returned to top level from NSolve @J.M. thanks for the link. No, I did not know about those other methods. Mar 22 comment My NIntegrate expression returns a wildly inaccurate value please post valid Mathematica code. The above hard to read. What is h = 100.0 i11 = a1xNintegrate? and a1xNintegrate ? Mar 21 comment Can one license be used on a dual-boot machine? This was asked before same-mathematica-9-1-student-license-on-both-ubuntu-and-windows-7 Mar 18 comment Differential equation and For loop in Mathematica But you wrote For[u == 1, u <= 1, so how do you expect this to run 11 times? try may be For[u = 0, u <= 1..... (note also difference between = and ==). These are not the same in Mathematica. see help on reference.wolfram.com/language/ref/For.html also better to use Do if you need to make explicit loops. Feb 6 comment Problems with QueueingNetworkProcess Your code is not valid actually. You are calling the function using shoppingProcess[s_]. This should be the definition of the function, not in the call. In the call, do not use _ on the argument. Feb 6 comment Fourier-style solutions to differential equations, not piecewise polynomials I do not understand the problem. Can you show an example where you could not differentiate InterpolatingFunction returned from NDSolve? But you could always find the Fourier series approximation of the InterpolatingFunction returned If this is what you want. It will not be any better than piecewise polynomials, due to Gibbs phenomenon to start with. Jan 31 comment Non Standard Eigenfunction Plots of the Laplacian Over the Unit Square fyi; Here is a demo that also plots the modes demonstrations.wolfram.com/VibrationOfARectangularMembrane Jan 31 comment Symbolic derivatives and substitution What you say should be the result is actually wrong. Try D[x h[x, y], {x, 2}] to see. btw, it might be easier just to make a function. r[expr_] := D[expr, {x, 2}]; then you can do r[f[x, y]] and r[x h[x, y]] Jan 31 comment How to plot points in 2D without restricting their apparent positions to pixel grid? You also defining a function use =. This should really be =:. Jan 31 comment How to plot points in 2D without restricting their apparent positions to pixel grid? There is no difference. Both "vibrate" the same way. Try this to see it better Manipulate[ Row[{ Graphics[ {PointSize[Large], Point[{0, x[t]}]}, PlotRange -> {{-0.1, 0.1}, {-0.1, 1.1}}, Axes -> False, ImageSize -> 50], Graphics3D[{PointSize[Large], Point[{0, x[t], 0}]}, PlotRange -> {{-0.1, 0.1}, {-0.1, 1.1}, All}, Boxed -> False, ImageSize -> 50, ViewVector -> {0, 0, 10^4}] }], {{t, .1, "time"}, .1, 100, .1, Appearance -> "Labeled", ContinuousAction -> True}, ControlPlacement -> Left, Initialization :> ( x[t_] := Abs@Sin[t]/t ) ] Jan 17 comment What are some “real-world” applications of Mathematica? Related question has answers here mathematica-application-in-real-life Jan 17 comment What are some “real-world” applications of Mathematica? Wolfram alpha is a real world application written in Mathematica: The secret weapon that has allowed us, and no one else, to assemble such a vast library of algorithms, in such a diverse range of fields, is Mathematica. from the-secret-behind-the-computational-engine-in-wolframalpha also half of Mathematica itself is written using Mathematica. I think about 50% is C/C++ and the other half is in Mathematica. This might have changed in recent versions. I remember reading this sometime ago. Jan 11 comment Order of evaluation - does Mathematica evaluate variables before or after substitution? Each symbol can have a value associated with it or not. When you write y=x^2, then later on, write x=10, then y now automatically becomes 100 since it was pointing to x before, but now x has a value which is 10. There is no explicit evaluation of y. It is done automatically. It is all linked lists. If a symbol x has value other than itself, then its value is used automatically when looking up y. Jan 11 comment How to fill in missing points on a graph? If you add PlotTheme -> "Classic" then you will not notice this. Jan 11 comment What's is the restrictions for the function MatrixExp? from help works only on square matrices. So as long as the matrix is square, it will work. Jan 11 comment Plotting x^(1/3) (-8)^(1/3)=-2, How did you get this? it is complex number? Jan 9 comment new kernel crashes using DSolve in 10.3.1 Thanks for trying. It crashes all the time on my Mathematica. May be there is something different in my system. Using service pack 1, windows 7. On fresh kernel. I can reproduce this all the time. I wish there is a dump file or some other log that the kernel writes when it crashes. This is very annoying that there is no log or dump file generated to look at. Jan 9 comment new kernel crashes using DSolve in 10.3.1 @b.gatessucks thanks for checking. It must be a windows only issue then. I am using windows 7, service pack 1, 64 bit.