Wolfram Mathematica

### How to eliminate the backward play in Export of Manipulate?

I find that the Export of Manipuate contains backforward play, see a simplified example: Export, {x, 0, 10}], {φ, 0, 2 π}]] You can see the problem in the SWF file. (I'm sorry that the exported SWF file cannot be uploaded here) Actually, I have two questions here, Is there .... Miles: 20 hours ago

Wolfram Mathematica

### Is there a way to convert a string to a Table indicator?

I have a list like this: list = {"k1","k2"} I want to use the elements in the list as Table indicators: Table], 1, 2}, {ToExpression@list], 1, 2}] but I get an error: Table::write: Tag ToExpression in ToExpression]] is Protected. Is there a way to get the right answer like: Table .... Jaxson: 20 hours ago

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### NDSolveValue::bcedge: Boundary condition is not specified on a single edge of the boundary of the computational domain

I'm solving a Schrödinger's Equation in 1d, where $\Omega$ is the domain, bcs the periodic boundary condition, init the initial condition. eqns = {I D, t] == -1/2 D, x, x] + 1/2 (x^2) ψ}; Ω = Interval; bcs = {ψ == ψ}; init = {ψ == Exp}; sol = .... Gabriella: 22 hours ago

Wolfram Mathematica

### Colorize a 3D distribution of points according to density

Suppose we have some random 3D distribution of points. I'll use the spherical ball defined below as an example and a starting point for the discussion here : Ball:=TableCos, #1 SqrtSin, #1 #2 } &], Random, Random ],{num}] Graphics3D,Point]},Boxed->True,BoxRatios->{1,1,1},ImageSize->800,SphericalRegion->True] This code produces the ball shown here : I would like .... Oliver: 23 hours ago

Wolfram Mathematica

### Find convenient numeric solution to intersection contour?

Consider the following contour of intersections between two analytic expressions: ContourPlot (x^2 + Cosh y^2) == y^2, {x, -1, 1}, {y, -2, 2}] The above nicely visualizes the intersection set, and also implies that the implementation of ContourPlot contains a very efficient algorithm that evaluates the intersection region numerically before .... Victoria: 23 hours ago

Wolfram Mathematica

### the number of values problem

I have the following problem. I have to generate 100 random values and make a list. From this list I will randomly select 60 values and calculate MeanCI <- This procedure must be repeated 100 times. I have to calculate the ratio between intervals MeanCI in which there is zero .... Amara: yesterday

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### Solving Cahn-Hilliard equation: LinearSolve: Linear equation encountered that has no solution

I have built the Cahn-Hilliard Eqs. in MMA (Mixed Formulation, second order), However, it doesnot work in MMA using Finite Element. LinearSolve: Linear equation encountered that has no solution. And "... are not the same shape". Theory & numerical formulation based on this FEniCS Benchmark Test enter link description here .... Jaxon: yesterday

Wolfram Mathematica

### How to find disjoint subsets such that union of the sets give the motherset or main set?

Let us define a set $\mathcal{S}=\{1,2, 3,\cdots,67\}$. I have a list of 132 subsets. I want to obtain 16(or 17) mutually exclusive subsets such that union of such 16(or 17) is equal to $\mathcal{S}$. In the case of 17 subsets, 2 subsets will have one element in common. Here is .... Hailey: yesterday

Wolfram Mathematica

### Speed up iteration of pair of fully coupled recursion equations

I am trying to do several hundred iterations of these fully coupled recursion equations (but will use twenty iterations for the example). ClearAll x1 := x1 = (1 - m) x1 + m x2 x2 := x2 = (1 - m) x2 + m x1 x1 := 1 x2 := .... Kai: yesterday

Wolfram Mathematica

### How to calculate arbitrary area on surface of sphere?

I am trying to calculate the solid angle (https://en.wikipedia.org/wiki/Solid_angle) subtended by arbitrary-shaped loops on a sphere's surface. First, I parametrize circular loops by: $$\theta(t,k_{x0},r) = k_{x_0} + r \cos(t);$$ $$\phi(t,k_{y0},r) = k_{y_0} + r \sin(t);$$ where $0\leq t\leq2\pi$, and $k_{x_0}$, $k_{y_0}$ define the loop's center. So, we can say that .... Amelia: yesterday