0
votes
0answers
29 views

How to solve the following fourth order partial differential equation including Laplacian

I wish to solve the following fourth order partial differential equation including Laplacian with the boundary conditions with the initial conditions ...
1
vote
1answer
16 views

Customized FortranForm output

Let's take the following example V = (-G*Mn)/Sqrt[x^2 + y^2 + z^2 + cn^2]; Vx = D[V, x]; FortranForm[Vx] The result is ...
2
votes
2answers
19 views

Export NDSolve results

I can see the correct result of my NDSolve when I plot them with large PlotPoints. ...
0
votes
0answers
12 views

Implicitly defined compact complicated surface

A Seifert surface for the (3,4) torus knot is defined by the intersection of $S^3 \subset \mathbb{C}^2$ with the set $\arg(z^4-w^3)=0$. The boundary is at $z^4=w^3$ and this is the torus knot. Here ...
0
votes
1answer
118 views

Solving differential equation with initial conditions

I want to solve the following differential equation with initial conditions: ...
2
votes
0answers
28 views

Calculation of 2D FFT for an image

I am trying to obtain 2D FFT of an image. From the 2D FFT, I wish to calculate the amplitude of the FFT averaged over a circle vs the distance in pixels by varying the radius of the pixels which is ...
0
votes
0answers
12 views

Large data plotted using ListContourPlot like in the attached figure

The following data had been used to plot the attached figure I want to know the method used to plot it? using the share like for data https://www.dropbox.com/s/balgkqslywf9kk5/data.nb?dl=0
2
votes
2answers
69 views

How to Optimize Solution? (Project Euler #14) [duplicate]

Link to Question: https://projecteuler.net/problem=14 I began by defining the following functions below. ...
355
votes
13answers
74k views

Where can I find examples of good Mathematica programming practice?

I consider myself a pretty good Mathematica programmer, but I'm always looking out for ways to either improve my way of doing things in Mathematica, or to see if there's something nifty that I haven't ...
0
votes
0answers
8 views

Mathematical formal expression of find “subfunction” in function [migrated]

Imagine if I have a function $s(t)$ and $r(t)$. $s(t)$ may contain $r(t)$ one or more times as $s(t)$ is a quasi-period function. What is the correct expression if I want to say the $s(t)$ contains ...
2
votes
0answers
63 views

Converting integral equations to differential equations

I am trying to use Mathematica to convert integrals to differential equations, of any order. An example of an integral equation is given below, in Mathematica code. Could you please advise as to the ...
5
votes
0answers
118 views

Wavelet Transform Modulus Maxima (WTMM) method

Has anyone already coded the Wavelet Transform Modulus Maxima (WTMM) method for computing the singular spectrum using multi fractal formalism in Mathematica? The goal is to analyse 1D, 2D and 3D ...
2
votes
2answers
85 views

Initializing several values of a function

How do I initialize several values of a function at once? Consider the function f[0] := 1; f[1] := 2; f[2] := 3; f[n_] := f[n] = f[n-1] + f[n-2] + f[n-3]; Is ...
4
votes
0answers
55 views
9
votes
1answer
71 views

How to disable half-hiding output, when the corresponding input cell is modified

I think it has become less easy to compare the new output, now that the output font color turns gray as soon as something is modified in the input cell. Is there any solution?
3
votes
1answer
41 views

Split/unmerge merged cells in notebook file

I have merged cells in a Notebook file. Is there a way to split such a merged cell group back to single cells, in each of them being one command?
8
votes
0answers
80 views

How can I smooth a 3D surface generated by RegionBoundary?

I have a set of points that belong to the surface of an object. I would like to approximate a surface to which I can compute the distance. of other points. With the nice code of this post, I was able ...
-4
votes
0answers
24 views

Creating eigenvalues of a matrix [on hold]

How do I store eigenvalues of a matrix in a For loop into a two dimensional array and then plot that array?
3
votes
0answers
32 views

Why is the Max function so slow when operating on lists of dates?

Example: dates = DateRange[DateObject[], DatePlus[DateObject[], 15]]; First[AbsoluteTiming[Max[dates]]] (* 21.364247 *) As a workaround, ...
0
votes
1answer
48 views

Calculate area from `RegionPlot` directly

I have a region plot, and I would like to calculate the area: ...
13
votes
5answers
1k views

How do I obtain the enclosed area of this particular parametric plot?

I'm trying to find a way to obtain the enclosed area of this particular plot. Can someone show me how? ...
4
votes
2answers
96 views

Reject diverging solution of NDSolve

I'm trying to numerically simulate a spring system with complex stiffness. In essence systems of the form $x''(t)+ (a+ ib) x(t)=0$ For this simple example an analytic solution is easy to find. The ...
1
vote
1answer
77 views
3
votes
0answers
36 views

AppendTo or Part in a ParallelDo?

I have a question regarding how memory is managed in parallel. Specifically, I'd like to know what is the better practice when constructing an array within a ...
0
votes
0answers
150 views

NonlinearModelFit giving message NonlinearModelFit::nrlnum: [on hold]

I'm trying to fit my data using NonlinearModelFit, but I keep getting errors that I don't quite understand how to correct ...
6
votes
1answer
130 views

Defining a function implicitly and calculating its derivatives

I'm interested in using Mathematica's symbolic manipulation to obtain, for a particular function $f$, derivatives of arbitrary order evaluated at zero. Normally I'd use the ...
1
vote
0answers
84 views

How I can integrate $\int_0^{a} x e^{-\frac{b^2 x^2}{2 c}} J_0(n x) dx$?

How can I get a solution to the integral given below ? $\quad \quad \int_0^{a} x e^{-\frac{b^2 x^2}{2 c}} J_0(n x) dx$ where $a,\,b,\,c$ and $n$ are constants and $J_0$ is a Bessel function of the ...
1
vote
1answer
27 views

A single point moving at different speeds through different regions on a plot (Manipulate)

I've been working on this for a while with little success. I have a point (that needs to be connected to a Manipulate control in some way), that moves up the plot ...
0
votes
3answers
47 views

NSolve not solving [on hold]

I've been working on a Newton Cooling equation problem for my diff equ class and cannot get NSolve to solve this equation. I've plugged it into Wolfram Alpha and my ...
5
votes
2answers
575 views
0
votes
1answer
67 views

FullSimplify not giving me a physically useful answer for Mott scattering

I am using Mathematica to find the cross-section for Mott scattering over an extended target. I evaluated ...
2
votes
0answers
29 views

exporting 3D graphics in STL format (for 3D printing) [duplicate]

How do I set the size of the exported item? (Graphics3D has no implied unit, so it is not a-priori clear what size the object will be, and experiment indicates that ...
0
votes
1answer
46 views

A question about the syntax [on hold]

I have $3$ elementary questions to ask and I thank you in advance. Question N°1. What is the right syntax for $$y\equiv0\pmod {2}$$ in the code below? ...
1
vote
1answer
52 views

Large data -list contour plot -list log plot

I've a large data make matrix 100*100 and and other two sets of data represent the x and y axis. Each value in the matrix is a related to one value in x and one value of y. I ask about a way to plot ...
2
votes
1answer
91 views

Unexpected results from GARCH Processes

I'm playing a bit with Time Series and I've been trying to estimate Garch Processes from different time series. Are TimeSeriesModelFit and ...
3
votes
1answer
150 views

Factoring the imaginary unit

Suppose you have this: Collect[2 u + I + 2 + I,I] It gives the same. Is it possible to factor I in elegant way (not ...
2
votes
4answers
142 views

Given a matrix of integer, create a matrix with 1 or 0 according to which numbers are in the first matrix

Not sure the title gives the idea of what I need, so here is a sample: I have ten (w) combinations (subsets) of 20 (n) numbers taken 4 (k) at time. I need a matrix of dimension w x n with 0/1 in each ...
0
votes
0answers
95 views

contour plot (cartesian) using spherical coordinates postions

Let´s say that I have a data in the following configuration: { Lat, Long,distance, energy}-> lat, long -> galactic coordinates, distance unit - parsecs (3.2 ly) energy unit- ergs. I need to plot ...
0
votes
1answer
98 views

Appending elements to a list in parallel table

Is there any way to store values in a list that is being computed in parallel? For example, if ParallelTable is computing some ...
5
votes
4answers
584 views

Finding number of pixels with certain RGB color in an image

I have the following image: To determine the number of black pixels (nBlackPixels) I use: ...
18
votes
1answer
272 views

How to use the Testing Notebook to test a package?

I think an important purpose of the new Testing Notebook in version 10 should be to test user packages (instead to test the builtin functions in the ...
1
vote
2answers
186 views

Problems finding intersection points between line and generic function

I'm trying to find Intersection points between a line, which is given by 2 points, and a generic function (I want it to be able to handle polynomial functions, circles/ovals, lines and all ...
-1
votes
0answers
26 views

NonlinearModelFit errors and precision [on hold]

unfortunately this question includes a lot of code. Sorry in advance. I use a data set, which I've made available here: ...
2
votes
1answer
45 views

Error accumulation in NDSolve?

I'm trying to solve this system of ODEs numerically: $$\vec{Q} = \vec{P} \times \vec{Q}$$ where vectors $\vec{P}, \vec{Q}$ have 3 components: $$\vec{Q} = \left( Q_1, Q_2, Q_3 \right) $$ $$\vec{P} = ...
2
votes
1answer
105 views

Equation involving hypergeometric functions

I want to solve this equation but nor NSolve nor Solve are able to do this. ...
14
votes
3answers
605 views

Nearest neighbor search in n-dimensions

Suppose a list of items such as: L1 = RandomReal[{0, 100}, 1000]; I need to find the position of each k-neighbor in the original list. And very quickly if ...
10
votes
1answer
118 views

Using Simplify on a consistent system returns False

Bug introduced in 8.0 and persisting through 10.1.0 or later It's late, but am I missing something here? Why should two independent equations, which together are consistent, ...
1
vote
0answers
50 views

How to use Wolfram language in an external program with low latency?

Im using Wolfram language on Pi B,and I want to compile a '.m' file (like "test.m" that contains Wolfram functions), in an external program like a C/C++ and then Export the output in an image file ...
5
votes
2answers
85 views

Can the increment in Manipulate, Table, Range, etc. be subject to an If statement?

In this demonstration I'm working on, I would like to plot a piecewise function with the tangent line to the function at a point that is determined by c in the code ...

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