0
votes
0answers
3 views

Partial derivative with Dirac Delta as initial condition

I am trying to reproduce the Faynman-Kac results from this Wikipedia page: Faynman-Kac This is the equation that I am trying to solve: $$ \frac{\partial w(t,x)}{\partial t} = \frac{1}{2} \frac{\...
0
votes
0answers
12 views

Finding all the distinct pairings of the elements of a set

I create a list of the first 23 letters of the alphabet, then I want to find all the distinct pairings, but I'm getting pairs where element1 == element2. How do I ...
1
vote
1answer
13 views

Increasing the thickness of a 3D surface

I am drawing a 3D surface with the following code: ...
0
votes
0answers
22 views

FindRoot with Inequality on Co-domain?

I'm hoping to implement a FindRoot procedure with an inequality constraint. However, I'm hopelessly confused at this point, because the inequality doesn't ...
2
votes
0answers
15 views

Max Size for SemanticImport?

Does anyone know what the max data size for SemanticImport is? I have a 4GB data file I need to break down, just don't know how small I have to break it. Thanks!
0
votes
0answers
5 views

sequence and comparison test [migrated]

is the sequence (((-1) ^ (n+1)) * n) / (n + sqrt n) convergent or divergent? I used comparison test, and I compared it with (n / (n+ sqrt n)). As lim n -> infinity, (n / (n+ sqrt n)) -> 1. So (((-1) ...
1
vote
0answers
27 views

t-SNE visualization

Is there an implementation of “t-SNE” for dimension reduction in mma? This technique visualizes high-dimensional data by giving each datapoint location in a two or three-dimensional map. It generally ...
0
votes
0answers
18 views

Possible bug with Testing Notebook & messages x::y where x has an OwnValue

I think this should be considered a bug (or at least an inconvenience) and should be reported: Say you have some code generating the $RecursionLimit::reclim2 ...
0
votes
0answers
13 views

Variating the derivative of the metric using xTensor

I would like Mathematica to be able to use the following expression in a more complicated computation: \begin{equation} \tag{1}\frac{\delta{}g^{\alpha\beta}_{\;{},\gamma}\left(x\right)}{\delta{}g^{\mu\...
0
votes
1answer
37 views

Find a Matrix given a characteristic equation

How I can compute a matrix given the characteristic equation ? All I found are references and functions that do the exact opposite, but I know the characteristic equation and I need the corresponding ...
0
votes
0answers
33 views

LinearProgramming accuracy problem [on hold]

I am working with the LinearProgramming to solve my problem. I am using Simplex and RevisedSimplex methods. They are giving me drastically different results for the same parameters. Examples are ...
0
votes
0answers
26 views

“Tag list in … is protected error” Small question [duplicate]

I am trying to do something very simple. I just would like to construct a translation matrix where I can chose my translation parameters: ...
3
votes
3answers
93 views

Replace last part in a list if there is somewhere a 0 in the list

I have the following list of lists: l={{5,6,0,8,5,9},{8,4,4,3,5,8},{9,4,3,2,5,7}} now if there is a 0 in one of the lists mathematica should replace the last ...
1
vote
0answers
22 views

Manipulate arrays [duplicate]

I want to sort the array a = {{{1, 0, 0}, {1, 1, 1}, {0.5, 0.0, 0.5}}, {{-1}, {1}, {-1}}} in the following way: a[[1]] and <...
-4
votes
0answers
63 views

system with MATHEMATICA

Can you please help me solve this system of ODEs with Mathematica? f, g, h, ...
-3
votes
1answer
46 views

Calculate lesser value subject to conditions

which is the lowest value of c: if $a^2 + b^2 = c^2$ , and , $ab + ac + bc = 100$ As I solve this problem with mathematica edit these conditions are generated from a right triangle with hicks a ...
1
vote
2answers
33 views

Partial Sums of Fourier Series [on hold]

It does not want to plot anything? Please, help me understand why. Thank you ...
0
votes
0answers
37 views

Why does Mathematica not simplify products of symbolic powers?

Why does Mathematica not simplify products of the following type? ...
0
votes
2answers
79 views

Verify $\frac{a_{20}}{a_{20}+b_{20}}$ in Mathematica, May help me?

The solution of $\frac{a_{20}}{a_{20}+b_{20}}$ is $-39$ from the recursive system of equations : \begin{cases} a_{n+1}=-2a_n-4b_n \\ b_{n+1}=4a_n+6b_n\\ a_0=1,b_0=0 \end{cases} This is taken from $...
1
vote
1answer
42 views

How to extract the cycle lengths from a permutation [on hold]

I want to input: Cycles[{{1, 3, 5}, {2, 4, 6}, {7,8}}] and get something like: {3,3,2}, that is, a list of the cycle lengths in ...
0
votes
3answers
39 views

Change entire column of matrix using its own elements for calculations [duplicate]

I am aware that there are discussions here about multiplying rows or columns in matrices, but I cannot figure out what to do in the following two cases. I have a matrix, lets say ...
4
votes
1answer
61 views

Ticks at multiples of $\pi$ in SciDraw

I'm having some trouble getting the labels right in a SciDraw figure. More precisely, I want labels at half-integer multiples of $\pi$, and I want them as clean inline fractions (i.e. as $\pi/2$ and ...
2
votes
1answer
23 views

How to use a list to label a BarChart

I'm trying to add labels to the BarChart I have generated from a Dataset however, I seem to be stuck on a couple of points. ...
2
votes
1answer
38 views

Absolute positioning for label in plot3d

I want to place a caption at the bottom of a Plot3D graphic that doesn't move as I rotate the plot with the mouse. I have tried two approaches, neither of which is satisfactory. My first approach is ...
0
votes
0answers
23 views

p-form definition

I'm working with xTensor and xTerior package. I have to define a generic p-form on a manifold of generic dimension. Thus I write, for 1-form ...
0
votes
1answer
29 views

Find the minimum value of a parameter above which a function is unity for positive values of its variable

I want to find the numerical value of alpha in function (-E^-x α + E^-x x α)^2/(2 (1 - E^-x x α)^2) above which the function is unity for some positive values of ...
3
votes
1answer
104 views

Plot artifacts depend on replacement rule

I am using Plot to look at the eigenvalues of a matrix, and find that in some circumstances I get artifacts. For example ...
0
votes
0answers
50 views

How to combine the graphs? [on hold]

I have code such as graph=ConstantArray[0,{1,nel}]; I have a graphlist such as; ...
0
votes
0answers
36 views

Compiling matrix multiplication using a list of matrices

I'm trying to create compiled function which computes a list of Gamma matrices named GammaM and multiply them within the compiled code. ...
3
votes
1answer
35 views

Adding red dot to tip of trajectory animation under specific conditions

I have the following little bit of code that models a thrust force being applied to a point-mass, and was wondering if it's possible to add a red dot to the "tip" of the animated trajectory when ...
0
votes
0answers
24 views

Speed up evaluation of “ParameterErrors” from NonlinearModelFit? [on hold]

I am fitting my data to the analytic solution of a coupled differential equation with up to ten fit parameters. The fit itself takes 40 seconds however when I want to obtain the parameter errors, it ...
3
votes
0answers
35 views

Calculating e.g. Euler density or Riemann tensor's square for a given metric using xAct package

I have started to learn about the xAct package to do some general relativistic calculations and whereas there might be other codes available, I would like to get my answer in terms of this package's ...
0
votes
0answers
49 views

how can i solve non linear ode

How do I solve the following ODE in Mathematica? DSolve[x''[t] + x[t]^2 + x[t] == 0, x[t], t] Such that the answer is as shown: Instead this function gives a <...
1
vote
0answers
41 views

Derivative of a function with indexed variables

I want to show that $$ \mathcal{U}(\mathbf x)=\prod_{i=1}^n U_i(x_i) $$ is a concave function, where $$ U_i(x_i)=\frac{c_i}{1+e^{b_i-a_i x_i}}+d_i $$ and $a_i$, $b_i$, $c_i$, and $d_i$ are positive ...
0
votes
0answers
9 views

How to delete variable assignments in a sub notebook which is called from main notebook?

I have two notebooks; one main notebook which calls another notebook several times in a loop. I want to delete the assignments of variables in sub notebook which is called. Using ClearAll["Global`*"]...
-1
votes
0answers
21 views

Get the values from Dynamic ListPlot

My actual goal is the able to get the numerical values of Dynamic@data but I am failing to do so. I found that I can create a plot and extract the values from the plot. I did not see any example for ...
0
votes
0answers
36 views

Numerical Integration

for solving the following integral I have used two different methods. The first way answer is zero while the second one answer is very large. What is the best way to solve such integrals? ...
1
vote
1answer
60 views

Reversing the order of Outer

I'm trying to use a function with two slots that I want to map over lists of different lengths and I think Outer is the function I need to solve the problem. I tried the following example: ...
3
votes
2answers
84 views

Changing the default alignment of a ragged array in ArrayPLot

I want to make the digits from this output to print starting from the rightmost column. ...
3
votes
1answer
64 views

Issue with symbolic summation [duplicate]

Here is the sum: $$\sum_{j=0}^{n-1}r^{a+b}\cos^a\left(\frac{2\pi j}{n}+t\right)\sin^b\left(\frac{2\pi j}{n}+t\right)$$ Code: ...
1
vote
0answers
26 views

How to define inclusions in FEM/NDSolve?

I am trying to simulate the compaction process of hot mix asphalts and want to do this with mathematica's FEM libraries. How can I define inclusions in meshes (i.e aggregate particles in the binder) ...
0
votes
1answer
51 views
1
vote
1answer
48 views

Taylor series representation function? [duplicate]

Is there a built in Taylor series representation function in Wolfram Mathematica? For Example: ...
0
votes
1answer
58 views

NDSolve solution disagrees with initial conditions

I just solved a differential equation with NDSolve, and the behavior of the solution was not what I was expecting. In trying to track down where things went wrong, I plotted the solution function ...
2
votes
0answers
28 views

FindClusters and friends run out of memory

I have a 50k lists, each has 1024 real numbers and I wanted to cluster them, but then the kernel crashes from memory pressure: It crashes even with ...
1
vote
0answers
24 views

Is there a way to do ParallelMapIndexed? [on hold]

I need the know the index of the items I'm mapping my function at, is there a way to achieve this when using all the kernels?
3
votes
0answers
47 views

Generating a list of random numbers that follows a pattern

I'm a beginner to Mathematica. I'm writing a code to design a 4-bar linkage mechanism that traces a path in 2D space. I got the modelling done right, now I'm writing my own implementation of a genetic ...
0
votes
0answers
19 views

Partitioning a set with a condition and ability to change it?

I asked this question and there is nice answers but only the first answer permit us to change the condition to another if we want, but this answer use a brute force approach and we can't use a ...
1
vote
2answers
62 views

Create matrix using loop?

Here I have a list of numbers (900 numerical values) denoted as d1-1, d1-2, d1-3.....d1-30, d2-1, d2-2, d2-3........d30-30. I want to create a matrix (900x900) which is organized as the below picture. ...

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