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103 views

Beginners problem, Do Loop, Eigenfunction iteration

I am trying to find the first Eigenfunction of the Laplacian (in 1D), i.e. a solution of $$ u''(x)=k u(x)\\ u(0)=u(1)=0 $$ with minimal $k>0$ (in this trivial example, I actually know the analytic ...
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votes
1answer
501 views

Best Mac for Mathematica [closed]

I am looking to buy a new Apple laptop or desktop for running Mathematica. What Mac is best, especially if I want to run numerical simulations in Mathematica? (A similar question was asked a few ...
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votes
1answer
256 views

How to replace the value that include infinity?

Good day, I have the output A and I want to do some operation to A: A = {0, 1, 2} B = -Total[(#*Log2[#]& /@ A] when i run, has error : ...
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2answers
212 views

Taking log derivatives of data in Mathematica

We have two lists (vectors) of data, y and x, we can imagine x being time steps (0,1,2,...) and y some system property computed at each value of x. I'm interested in calculating the derivative of log ...
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0answers
149 views

Any way of solving this system of nonlinear equations with non integer powers?

I have a system of four nonlinear equations. Some of the exponents are fractions. I was wondering if this is what is causing NSolve to run for hours without giving ...
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1answer
323 views

Re[x] vs. x ∈ Reals in the context of Assuming

Let's say that $x$ is some real valued number $>0$. Are the following commands interchangeable in the context of using Assuming? ...
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2answers
411 views

Lagrange multipliers code runs forever

I am writing a code for a Lagrange multipliers problem with three variables. My code looks like this: ...
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0answers
55 views

non-intersecting cylinders and DiscretizeRegion, RegionIntersection [duplicate]

This is a sequel to my previous post. ...
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0answers
61 views

Capture/Save Manipulate[Select[dataset to Usable File Format

Using the following code generates a view of exactly what I was seeking, 'manipulating' a large spreadsheet/table: ...
0
votes
1answer
35 views

Wrapped Association into a “structure”: how to define Equal[] and what are the good practices for package dev?

Using a nice answer https://mathematica.stackexchange.com/a/197936/42847 I got from a previous question I define: ...
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0answers
31 views

How to create a function in mathematica to solve for 'x' for later use?

I would like to create the quadratic formula in mathematica, multiplied with the identity matrix 5. How to store it for later use? I would like to be able to input a,b,c when I later call the ...
0
votes
1answer
296 views

Extracting the contour lines from an image [duplicate]

The Image presented is created by Mathematica ListPLot. It's a list of points out of a 512x512 grid, which meets criteria. I would like to be able to identify the ...
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votes
1answer
135 views

Numerically solving two coupled nonlinear PDEs

I'm interested in numerically studying vortex solutions to PDEs. By this I mean solutions for PDEs for a field $\theta$ which satisfy $\oint\nabla\theta\cdot d\vec{\ell}=2\pi m$ where $m=...,-2,-1,0,1,...
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1answer
46 views

Complex infinity at a point and division by zero

Edit: I've found out that the book was written for Mathematica 7, which was a pretty long time ago. It boils down to changes in syntax most probably, but simple renaming to lower lettercase does not ...
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votes
2answers
192 views

Fraction of fibers that have failed

I have the following to set into mathematica. Assume a stress(sigma) applied on a specimen which has a number of fibers within it. All fibers that have a strength less than the applied stress should ...
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1answer
68 views

probability going outside 1 (due to optimization violation of constraint)

I am working on an optimization, which involves the following density: ...
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votes
2answers
81 views

Redirecting All Prints (including those in subkernel) to file

How do I redirect all printed text to a file instead of the FrontEnd? This question was answered in Temporarily redirect the output of Print[ ] to a second file, except that this does not capture text ...
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votes
1answer
104 views

`Plus` wrongly applies `OneIdentity` to eradicate itself in `Plus[Power[_, 2] ..]`, unreproducible

I was trying to match some polynomials, but this is weird: ...
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votes
1answer
132 views

How to find analytical solution for integral from product of Bessel functions of second kind with different order?

I need help with analytical solution for the following integral: ...
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votes
1answer
209 views

Colors on a 3D curve not working

I'm having troubles applying colors to a simple 3D curve plot. Here's the code : ...
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votes
2answers
116 views

Cases Message Valid Notebook Structure

Note: Spelunking will likely be needed. Execute the following. You should get back and error along the lines of First::first:... This error is unimportant except ...
0
votes
1answer
527 views

Plot table versus table [duplicate]

I have two tables like: nex1 = Table[l3*10^3/4*10^14, {l3, 1, 30, 1}]; nex2= Table[l4, {l4, 1, 30, 1}]; How can I plot nex1 versus nex2 so that nex1 is x axis ...
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votes
2answers
111 views

Product of large number with a very small number returns zero because Mathematica sets the very small number equal to zero [closed]

I have a product Exp[-I*Pi*x]*BesselK[-1, 2.43*Ix]. Now, Exp[-I*Pi*x] grows larger and larger as $x$ increases for imaginary ...
0
votes
1answer
82 views

Using multiple boundary conditions with NDEigensystem

I'm quite new to Mathematica and to Stack Exchange so I apologise if this question has already been answered. I've recently been trying to solve a partial differential equation to find the ...
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votes
1answer
83 views

Differentiating two tables x and y?

I have two tables x and y with x={673,674,675,...} and y={0,1,2,...} and delta=dx/dy. I would like to know how delta can be calculated knowing that delta is the derivative of x divided by the ...
0
votes
1answer
2k views

How to show legend in a combined plot of many lists,

I am having trouble with adding a legend to a plot. The example I discuss here is simpler than my real problem, but describes it well. I have a vector, called X with dimensions (100 x 6). I use the ...
0
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0answers
200 views

Simplify closed formula for distance-preserving great circle spherical coordinate parametrization

Short version: can the function paramLonLat defined below be simplified given the conditions conds below? Note that the return ...
0
votes
1answer
118 views

Problem simulating a wave on a string by solving the wave equation as a difference equation.

This is a question I posted earlier however the purpose of what I'm doing is going to be expounded much more clearly. ...
0
votes
2answers
283 views

Print expressions using local variables in Module without Dollar sign: is that possible

In a Module, I want to print the result of some data fit. I use something like this: ...
0
votes
2answers
104 views

How to draw two error bars at one point in Mathematica?

I have read the error bars reference in Mathematica to find how to draw a picture like the one above(The thick error bars indicates interval of 68% probability and the thin ones denotes 98%), but I ...
0
votes
0answers
103 views

FiniteElement and NDSolve won't work

I need to solve a system of DE's in 2 dimensions over time, The problem is that mathematica complains when I have a boundary condition of the same order as the differential order of the DE's, so I ...
0
votes
0answers
48 views

How to release a secure MMA-NB/CDF with restrictions/locks to the back-end code visibility

Intention is to distribute demonstration files just like Wolfram Demonstrations (mainly dynamic manipulations with assisting textual explanations based off on Numerical Methods course lectures). If ...
0
votes
2answers
434 views

How to draw multiple cuboids on the same plot

I have defined a table ...
0
votes
1answer
108 views

How to get an elements of given class that generated by javascripts

I want to get the number of total pages of a given search resluts of this site: http://srh.bankofchina.com/search/whpj/searchen.jsp, e.g., from 2015-1-12 to 2015-1-13 the currency of USD by the ...
0
votes
1answer
336 views

Display trigonometry without Csc and Cot [duplicate]

I have a result with trigonometry functions using Cot and Csc. I would like to keep only cos, sin and tan and so prefer fractions in the display of the results. How is it possible to ask Mathematica ...
0
votes
0answers
52 views

ListPointPlot3D small and large values [duplicate]

I am using ListPointPlot3D for visualizing the difference between two functions. The difference sometimes can be really small on the order of 10^-50 or smaller. There is cut-off where I can not see ...
0
votes
2answers
207 views

Approximate UnitStep for use in Enterprise CDF

The following Manipulate code displays the VectorPlot for all functions. (This code is a subset of a more extensive notebook which is based on the structure you see below. Consequently, I need to ...
0
votes
1answer
90 views

Point lattice leading to triangle lattice

My main purpose is to eventually generate a triangle lattice from one original point, let's say the origin. So I want to start with the origin and generate 6 points around it, which are the vertices ...
0
votes
1answer
82 views

Estimating parameters for pair of differential equations efficiently

I'm trying to estimate the parameters for the following pair of differential equations ...
0
votes
3answers
73 views

Sample the data with equal step size

I have the data below. I would like to sample with equal step size. For simplicity lets try unit step size. Here is the desired result. Find the first time exceed the unit time step, and take lower ...
0
votes
5answers
158 views

Find optimal integer solution to linear equation (Wolfram Alpha)

I'm sorry if this is potentially off topic, but I posted this question at the Math SE and they pointed me here. Both SE sites have a tag for Wolfram Alpha, but maybe you guys are better equipped to ...
0
votes
3answers
151 views

Saving many plots in files [duplicate]

I made a table of ten plots: Table[Plot[u[t, x] /. wws, {x, -10, 10}], {t, 0, 10, 1}] I want to save them all to my file system. I know, that I can save each ...
0
votes
1answer
1k views

Plotting Extended Zone Scheme:

How could I present an extended zone scheme for a delta-function Kronig-Penney model? That is, how can I display only the lowest contour in the region [0, π], the second-lowest contour in the region [...
0
votes
2answers
30 views
0
votes
1answer
263 views

Manipulate Cuboid for Rotation

Using the example code from the cuboid: ...
0
votes
1answer
105 views

Strange behavior of derivative when using Abs[] [duplicate]

This code where I try to visualize Newton's Method on the function $f(x)=\sqrt{|x|}$ works fine when I define $f(x)$ piecewise. Then why doesn't it work when I define ...
0
votes
1answer
111 views

Invert and fit implicitly defined curve

I need to fit an implicitly defined curve. I thought I could get some data out of Solve, and then using FindFit. Therefore, I ...
0
votes
0answers
38 views

Draw application: how to edit text and how to size the figure?

I read this previous post about the Draw application and tried to use it: Draw: vector drawing & technical illustration application The application's documentation is available here: http://...
0
votes
1answer
3k views

Discrete Fourier Transform: help on how to convert x axis in to the frequency when I have a set of data samples [duplicate]

I have a huge data set (400000 sample) and when I plot them ListLinePlot[Au4, PlotRange -> {All, All}] I used the following code to Fourier transform it <...
0
votes
0answers
51 views

How to accelerate NDSolve for PDE with user defined functions?

I would like to solve the following 2D+1 PDE $\partial_t \mathcal{P}(t,\theta,\omega)=-\partial_{\theta}( \omega\mathcal{P})+\partial_{\omega}\left[(\tau_i n\cos(n\theta)-\tau_m(\theta))\mathcal{P}\...

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