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4h
comment Poison PDE in rectangular domain
When the hole is also rectangular shape, then makes it easier, since the grid can be made to align there. with the rest of the region with no problem. So all what you have to do, is in the loop as you scan the region (updating the solution at each point), is simply check if you are inside the hole or not.
4h
comment Poison PDE in rectangular domain
If there is a hole inside the section, then it is not rectangular section any more. FDM is hard to use when there is circular or any other shape boundaries since the meshing becomes hard to get correct (some points end up outside and some inside, etc..).That is why I think FEM would be easier for this. But you really need to describe the geometry better. What are the dimensions? What is the hole shape? etc..
5h
comment Poison PDE in rectangular domain
if you want Poisson solver using FDM on rectangular cross section, there is a demo that implements this with many other solvers as well. demonstrations.wolfram.com/…
5h
comment How to check if two nested lists have the same structure?
I actually do not understand the question. But if you want to look into each dimensions itself, you can do Dimensions[list2[[1]]] and so on. Mathematica sees each list as having 3 lists in it. But each list itself can also have other lists inside it. and so on.
5h
comment How to check if two nested lists have the same structure?
Dimensions[list1]; Dimensions[list2] says the dimensions is the same.
6h
comment numerical integration with parameter
other than syntax, you can't do numerical integration with symbolic limit
7h
comment Laplace PDE in a polar coordinate system
This PDF shows what to do at $r=0$ to avoid blow up, which is to set one of the constant of integrations to zero. May be you can follow this derivation and apply your numerical solution to the resulting solution.
7h
comment How do I get the bounds of my Slider to correspond to the current length of a string entered in another control?
@raxacoricofallapatorius the solution uses the second argument of dynamic. I do not know how else to solve it, but there might be a way to do it without using the second argument of dynamics. I do not know.
8h
comment How do I get the bounds of my Slider to correspond to the current length of a string entered in another control?
@raxacoricofallapatorius I use LICEcap to record it from the screen as animated gif file. I hope someone can understand better the solution you need and provide better implementation. good luck.
21h
comment Convert a list of hexadecimal numbers to decimal
To automate this little more, may be FromDigits[#, 16] & /@ (ToString[#] & /@ u)
1d
comment FindDivisions behavior changed?
something is wrong here. docs shows your call should work as written. Last entry in help. !Mathematica graphics btw, I get same error in V 9 as in V 10.02
1d
comment Using Solve to obtain a constant so that f(x) is continuous at x=2
@user27386 Changed the plot command above to change the limit of the plot. Like this Plot[myfunc[x] /. c -> sol, {x, 0, 4}] or Plot[myfunc[x] /. c -> sol, {x, 1.9, 2.1}] etc... but if you want to zoom in and out, it is very easy to make a manipulate and use a slider to change the zoom level.
1d
comment Error message for FEMStiffnessElements
may be it does not like the complex part. (all those I's in there). Is this quantum mechanics problem? No beep sound is generated when the "I's" are removed.
2d
comment Creating a matrix under conditions
@asad I think it is ok now.
2d
comment How to solve this linear equation?
Just type eq = y''[x] + 6 y'[x] + 4 y[x] == x^2* Exp[2 x]; DSolve[eq, y[x], x] and you'll get the solution. it is linear second oder ODE.
2d
comment How to solve this linear equation?
I think you have mixed the dependent and independent variables in the early part of the ode. can you check again the book? I think it should be $\frac{dy}{dx}$
Mar
28
comment How can I simplify a triple integral with exponentials?
@smtux There was no need to use simplify? You could always do simplify at the end if you want, but in this case, the result do not change form and remain the same size.
Mar
28
comment How can I simplify a triple integral with exponentials?
@smtux Why do you have to change your code to handle these assumptions? Just use the code I posted. Does it have to be all in one line? To make it easier, I updated the answer and pasted all the code in one cell. So just use this cell instead of yours, that is all.
Mar
28
comment 4th-order Runge-Kutta method to solve a system of coupled ODEs
This post has code for Runge-Kutta solving-a-system-of-odes-with-the-runge-kutta-method
Mar
28
comment 4th-order Runge-Kutta method to solve a system of coupled ODEs
Can you show the equations themselves you are trying to solve with the initial/boundary conditions? If you do not know latex, you can scan them from the book and paste the image.