# All Questions

57,863 questions
98 views

### How to use Mathematica's Moment Generating Function?

Given the following p.d.f., which is the p.d.f. of the ratio between a complex Gaussian and a Chi-squared RVs: \begin{equation*} f_U(u)=\exp\Big\{{-\frac{1}{4 u^2}}\Big\} \,\frac{\left(8 n u^2-1\...
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### Rotation in physics

I have a mathematica problem in theoretical physics: There is a rotation axis $\vec{n}$ with $|\vec{n}|=1$. Each other vector $\vec{v}$ can be seperated in relation to $\vec{n}$ in a parallel part ...
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### Is it possible or how to extract message string from binarized list?

Given message copied from Silvia's profile page, a binarized list could be found bellow. ...
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### Trying to select data in a csv based on month

I have a csv file that has the measured data (conc), where it was collected (z) and date. I'm trying to select data based on the month it was collected in so I can plot them separately and compare. I ...
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### Function returned from module doesn't work [on hold]

I have a sequence of steps that work in the main notebook: ...
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### When using Mathematica Online, where are exported files saved?

I would like to 3D print some Mathematica-generated polyhedra, but I can't figure out how to download the files generated from the 'Export' command. For example: ...
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### ParametricPlot table of complex functions in several graphs

Assume that I have a table of complex functions like Clear[p] Clear[M] M = 10; G = Table[Sin[i p] + p I, {i, M}] I want to ParametricPlot them in graphs, each ...
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### OpenCL for symbolic matrix manipulations [on hold]

I want to calculate a matrix multiplication of matrices with a size of 500 for example, but all elements are symbolic. Since it is a bit slow with a normal way, and gets slower and slower with ...
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### When is the next release? [on hold]

I've been looking into buying a student version of Mathematica but saw the latest release was almost a year ago. The previous release cycle looked like it was every several months or so. I run Ubuntu ...
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### How to use DirichletCondition with DSolve and not just NDSolveValue?

I know one can use Region and DirichletCondition with NDSolveValue. But I do not know why it ...
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### Precalculating ThreeJSymbols to make my program faster

Does anybody have an idea what is the best way to pre-calculate the ThreeJSymbols in order to use them in a loop? (I want to make my program work faster that is why ...
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### A function to create a Symmetric Positive Definite Matrix, from any matrix. Why doesn't it work? [on hold]

I've created the following function with the purpose such that, given any square matrix, it should return the closest(system precision dependent) symmetric positive definite matrix. ...
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### Clustering different kernel versions

After a good bit of trial and error I have managed to cluster together two OS X machines. The master is running Mathematica 9.0 and the secondary 11.0. All was well and good, the remote command being ...
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### Using OverBarred variables

Mathematica does not seem to treat variables as a unit. Consider the following: rule = a -> Function[{x}, OverBar[a][x]] test = a[x] /. rule; test /. rule It ...
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### When computation takes a long time, how to find out if this is normal or if my script contains an error?

I study mechanical engineering and I' working on my first bigger project on Mathematica right now. It's a multibody problem that leads to a system of 4 large equations I'm supposed to solve ...
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### Solving a 2nd-order nonlinear differential equation [on hold]

My equation is [{x[t]*x'[t])'-(F/m)+(b/m)*x(t)*x'(t)==0},x(0)=0,x'(0)=0] It is a form of Newtons momentum equation, but I am having a lot of trouble solving this ...
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### Selecting from a matrix according to elements of a column — efficiency and speed?

I need to select all elements from matrix M that have in their 3rd column elements from some given list L (3rd column and L are real numbers). I have written the most obvious (to me) command to select ...
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### Errors while installing MatLink

I'm new to MatLink, I spent the last couple of hours trying to install Matlink but I did not succeed. When running Needs["MATLink`"] OpenMATLAB[] in ...
1k views

### Sisyphus Random Walk

A Sisyphus Random Walk evolves as follows: With probability (r) you advance the position of the walker by +1. With probability (1-r) the walker resets at x0 = 0. To simulate the probability of reset ...
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### Singularities forming on boundary while solving system of pde's

This is a follow up of a previous question I asked regarding solving a system of coupled, non-linear partial differential equations, 2D spatially + time. The equations (shown below) model a magnetic ...
671 views

### Set every element to zero in matrix unless it's 1 or 1/2

I have the following code: ...
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### How to define mixtures of random variables?

I am confused by the behavior of MixtureDistribution, even though that sounds like what I would need. Let's say I want to get a parametric solution for the ...
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### How to get the Roots of nonlinear equations

How to get the Roots of nonlinear equations. nu=326.531 Plot[(I*m1)*Tanh[I*m1] - nu, {m1, -1, 30}] How to get the first ten positive roots and i have tried ...