10
votes
1answer
673 views

Numerically solve 2nd order differential equation with singularity

Consider a second order differential equation with a potential that diverges at some generic value in the variable. For example: $$-y^{\prime\prime}(s)+\frac1{\mathrm{cn}{(s\mid k^2)}}y(s)=0$$ where ...
0
votes
0answers
20 views

MatrixExp[] of a complex matrix of size about 10000 by 10000

I used the MatrixExp[] of a numerical complex matrix of size about 10000 by 10000 and I also need high precision as I need to multiple several such matrices. It turns out to be out of memory during ...
1
vote
1answer
768 views

Integro-differential eqn with double integral

I am looking at the following variation of a integro-differential, with y[0]=1. The output is not great, any solutions to this? ...
0
votes
0answers
12 views

Differentiation inside pakage

I am trying to put all my functions in a single package and some of them do not work because of differentiation. Suppose I have the following package ...
1
vote
1answer
40 views

I keep writing functions like this one: subtract[{a_, b_}] := Subtract[a, b] [duplicate]

(Edited to provide an example) Recently I have found myself writing silly functions like the following, which is just a new arity of Subtract in which the arguments are inside a list. ...
0
votes
1answer
26 views

Colors on a 3D curve not working

I'm having troubles applying colors to a simple 3D curve plot. Here's the code : ...
1
vote
1answer
25 views

How to define a number of infix operators with predefined relative precedences

Reading a number of questions about infix operator notations I want to ask if somebody could reimplement the problem below in a simpler way, say modifying ...
0
votes
0answers
10 views

Trying to find parameters for a system of ODEs

So I have a system of 4-dimensional system of ODEs and I'm trying to find any values of parameters that satisfy properties I need. In this picture, I want two basins of attraction, one of which the ...
0
votes
1answer
57 views

NDSolve There are fewer dependent variables, {V[S,t]}, than equation

I am trying to solve the BlackScholes PDE for Barrier option. It works fine for european barrier, but errors out on american boundary condition ...
1
vote
2answers
100 views

intermediate steps of a Mathematica operation

How to make a multiplication or division, the intermediate steps. The numbers can be rational - decimals? it seems the OP merely wants Mathematica to show him how to multiply and divide the way ...
0
votes
0answers
15 views

Selecting the parallel kernels where tasks can be executed

When I use ParallelSubmit, is it possible to select on which kernel a task can possibly be executed ? For example if have 3 parallel kernels, can I only use 2 of them so that one is remaining in case ...
5
votes
2answers
264 views

How to improve visualisation of trajectories in 3D space

I have a list of trajectories from a bunch of photons that travel inside a scattering medium. Each trajectory is a list of $(x,y,z)$ pairs. I'd like to visualise them in 3D space. I came up with the ...
2
votes
1answer
54 views

Adding extinction factor to Monte Carlo analysis

I'm looking to add an absorption component to this Monte Carlo analysis, essentially I want there to be a 1% chance that a photon gets absorbed at each event as it travels through the medium, once the ...
2
votes
1answer
337 views

Summation of If statements

The following made me curious. Suppose you want to sum the if statement If[x[i] < 1., x[i]^2, 0.] over i=1,2, i.e. ...
8
votes
0answers
46 views

Is this behaviour, producing OutputSizeLimit`Dump`encapsulateOutput, a bug?

Bug introduced in 6.0.0 and persisting through 10.2.0 The input ...
0
votes
0answers
21 views

Real time solution of a DE with changing parameters

I have a set of coupled differential equations (9 equations with 9 unknowns) and 9 known initial conditions to describe the motion of a quadcopter. Question: how can I make a real-time simulator out ...
1
vote
1answer
21 views

Associations - getting values according to a key pattern

I want to get all counts of trigrams that with "th" (or any other given digram). ...
3
votes
1answer
140 views

Trouble with polynomial multiplication

Bug introduced in 10.1.0 and persisting through 10.2.0 or later ...
19
votes
3answers
817 views

How is + as an infix operator associated with Plus?

How is + associated with Plus? Suppose I want to define a head FooBar and have it ...
0
votes
0answers
16 views

How to import a Graphs & Networks graph as a Mathematica graph?

This graph (as a picture) is given below: I am wondering rather than setting up this network graph using Mathematica syntax such as PathGraph,...
16
votes
2answers
279 views

How to implement the sample-point process like the built-ins of Mathematica?

Considering that pts = {{0, 0}, {1, 1}, {2, -1}, {3, 0}, {4, -2}, {5, 1}}; f = BSplineFunction[pts] Then I can use ...
1
vote
1answer
60 views

Program to demonstrate rotation according to quaternion values

On the Wolfram|Alpha website, I type quaternion(1,1,1,1) into the search field. Wolfram|Alpha shows a 3D transformation of the quaternion values representing the orientation of an object. I have 9 ...
0
votes
0answers
30 views

Gradient Help w/ Problem 1 [on hold]

​Go with f[x, y, z] = Log[3 x^2 + y^2 + z^2] In which direction should you leave the point {2.1, -3.7, 4.3} to get the ...
11
votes
1answer
141 views

Global` context not empty at startup in v10.2.0

Bug introduced in 10.2 and persisting through 10.2 or later Note that the analysis of this problem revealed a different problem than in Potential pollution of Global` context in fresh kernel (see ...
6
votes
2answers
147 views

Number of divisors visualized with the QPochhammer function, how improve performance of code?

I have this code that is originally Jeffrey Stopple's code for the Riemann zeta function in the complex plane. Because I discovered yesterday that the number of divisors can be generated with the ...
7
votes
3answers
575 views

Only final result from NDSolve

Finally I started to play with differential equations in Mathematica. And I have faced the problem, which seems too me so basic that I'm afraid this question is going to be closed soon. However, ...
0
votes
1answer
43 views

thickness of plotting edges

used these codes to might a simple triangle, which nodes have different effects each other: ...
0
votes
0answers
16 views

Custom drop-down list of tags for Dataset Keys similar to CountryData

CountryData produces a drop-down list of tags when you enter a string. I would like to replicate this functionality for a ...
15
votes
3answers
332 views
+100

Returning multiple results from a LibraryLink function

What is the best way to return multiple inhomogeneous results from a LibraryLink function? Imagine that the result of a single computation is several tensors of different dimensions and several ...
10
votes
0answers
181 views

Possible bug with FourierTransform linearity

Each component is easily transformed but the sum is not: FourierTransform[f''[x], x, k] FourierTransform[f'[x], x, k] ...
1
vote
1answer
77 views

How to find a cycle with a property in a graph

Let's have a graph with this edge list: edgelist = {s -> 1, s -> 2, 1 -> 3, 2 -> 1, 2 -> 4, 3 -> 2, 3 -> t, 4 -> 3, 4 -> t}; I want ...
3
votes
3answers
476 views

Efficiently compute double sum

Is there a "Mathematica Way", like Map or Apply to compute the following double sum? $\sum_{i=1}^{N_1}\sum_{j=1}^{N_2} m_i n_j \, f(\tau_{i} \gamma_{j})$ I have already stored the lists ...
1
vote
2answers
77 views

How to get the desired (equivalent) answer from Integrate?

This is the integrand: 1/beta/(2*z)/(1 - beta) // TraditionalForm Integrating with respect to z, gives ...
12
votes
2answers
571 views

Where is the “Function Navigator” and “Virtual Book” gone?

Under V9 "Help" was a Item each for "Function Navigator" and "Virtual Book" to find and one could work with it. Under V10 these Helpers are gone. Although under Documentation/English/System the ...
3
votes
4answers
197 views

Trouble with Position[] [duplicate]

I am in trouble with Position, Although my example works as expected it throws a warning. Position[{{a,b},{a,c},{a,b}}, _?(#[[2]]==b&), {1}] During ...
5
votes
2answers
110 views
+50

What's the difference between Interpolation[pts, Method -> Spline] and BSplineCurve?

Last month, I answered a question about spline interpolation,please see here Now I do the following operations ...
12
votes
2answers
345 views

Interpolation on a regular square grid spanning a triangular domain

Bug introduced in 10.0 and fixed in 10.1 Context I am trying to identify contours of a function which is sampled on a cartesian grid within an irregular (triangular) region. Here is the data ...
4
votes
1answer
68 views

upper limit with `PlotStyle` in `GeoListPlot` in v10.1

Bug introduced in 10.0 and fixed in 10.2 Let's start with the code below: ...
0
votes
2answers
39 views

“Part specification is longer than depth” warning in Position function [duplicate]

I'm working on a project which analyzes financial data. I download the price and dividend information for the SPY ETF which tracks the S&P 500: ...
8
votes
2answers
130 views

Difficulty using LUDecomposition

I'm having trouble using LUDecomposition with pivoting. I read the Mathematica help on this particular command, but I'm still lost. Take a matrix like: ...
0
votes
0answers
59 views

JacobiCN inaccuracy [on hold]

For my calculations I need JacobiCN[s,k] for s near 0 from the left and k near 1 from the ...
1
vote
1answer
57 views

Same scale for all the axes in Plot3D

I can't find this in the documentation. How do you force the same scale for all the axes when making a 3D plot? There is the BoxRatios option, but this only changes ...
2
votes
2answers
77 views

Displaying a list of percentage values according to their classification

I have a list of percentages as follows: percent = {21.15, 42.3, 57.68, 73.06, 84.6, 90.37, 96.14, 99.99, 99.99, 99.99, 99.99} I want to classify these ...
0
votes
1answer
45 views

Numerical integration with assumptions

I have to numerically integrate an integral with two variables r and v, but I want to do the evaluation assuming ...
29
votes
2answers
2k views

Playing with Matrix falling code in Mathematica

I was trying to create a Matrix falling code image with Mathematica. Here is my code: ...
0
votes
1answer
347 views

Mathematica Implementation of Householder’s Method

I typed the Householder code in this paper, which starts on page 7. The code is: ...
5
votes
1answer
599 views

How to implement Kemeny-Young method? (rank aggregation problem)

Prehistory I am trying to make some statistical analysis of some experimental data, arises from measurements made ​​on an ordinal scale. I faced with the problem of rank aggregation: to get from ...
0
votes
0answers
146 views

step by step interactive indefinite integral

WolframAlpha can give step by step solution for indefinite integral. There seems to be similar question but for derivatives. Is there a way that I can generate my own step by step solution for ...
3
votes
3answers
251 views

3D Gamma function

I try to plot the following function: Plot3D[Gamma[1+0.5*(n+m)]/Sqrt[Gamma[1+n]*Gamma[1+m]],{n,0,1000},{m,0,1000}] I expect that for m=n and near to it the value ...
8
votes
1answer
160 views

How to change the font color of a variable in whole input cell

I want to track the occurrence of a particular variable in a code. So the idea is to change its color. Usually I do it in a crude way - convert the code into text and then use ...

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