0
votes
1answer
10 views

Calculate area from `RegionPlot` directly

I have a region plot, and I would like to calculate the area: ...
12
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? ...
0
votes
0answers
8 views

How to Optimize Solution? (Project Euler #14)

Link to Question: https://projecteuler.net/problem=14 I began by defining the following functions below. ...
3
votes
2answers
38 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
52 views
2
votes
0answers
17 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
148 views

NonlinearModelFit giving message NonlinearModelFit::nrlnum:

I'm trying to fit my data using NonlinearModelFit, but I keep getting errors that I don't quite understand how to correct ...
3
votes
1answer
31 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
40 views

Converting integral equations to differential equations [on hold]

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 ...
1
vote
0answers
52 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
18 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
45 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 ...
4
votes
2answers
571 views
0
votes
1answer
56 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
26 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
38 views

A question about the syntax

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? ...
0
votes
1answer
39 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 ...
1
vote
1answer
88 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
120 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
120 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
89 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 ...
2
votes
0answers
24 views
0
votes
1answer
92 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
390 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: ...
5
votes
0answers
46 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 ...
18
votes
1answer
267 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
184 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
23 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: ...
3
votes
1answer
26 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?
2
votes
1answer
38 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
603 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
115 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, ...
0
votes
0answers
33 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
82 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 ...
0
votes
0answers
34 views

Import 3D Jpeg file [on hold]

How can I import 3D jpeg file to Mathematica ? I would like to import it and save it into a 3D pdf format. This is the images
0
votes
0answers
39 views

Defining A Function With A Certain Domain

I am trying to plot the numerical range a matrix, which is a set defined like so: $W(A) = \{\langle Ax,x \rangle : x \in \mathbb{C}^n \text{ and } ||x|| = 1\}$ In other words, I am trying to plot ...
7
votes
3answers
209 views

Copy/Pasting a Grid of Numbers from Project Euler

On Project Euler Problem 11 (link: https://projecteuler.net/problem=11), there is a 20x20 grid of numbers. However, when I pasted it into Mathematica, I got this strange result where the times symbol ...
0
votes
2answers
58 views

Write list of numbers to a file

I have a list of numbers: e.g. list={1,2,3,4,5} To write the list to a file I use (here each integer number occupies 7 spaces): ...
-1
votes
0answers
19 views

How to compare strings insensitive? [on hold]

To compare str1 with str2 I would do StringMatchQ[str1, str2] What if I want the ...
1
vote
0answers
67 views
0
votes
1answer
29 views

How can I move the x-axis label beneath (instead of at the end of) the x-axis?

I borrowed this code from a Wolfram demo. I looked at several answers to the general question of how to move the x-axis label from the end of the x-axis to beneath it (use ...
0
votes
1answer
42 views

Plotting based on all previous equation results [on hold]

I have a plot Plot[40500*x^(-0.1), {x, 1, 100}, PlotRange -> {0, 50000}] Now, I am trying to plot the cumulative of these y values. I'll try to explain on an ...
3
votes
3answers
120 views

Calculating $\lim_{x\to 1} \, \int -\frac{i \text{Li}_2\left(x-x^2\right)}{\sqrt{3} \left(x-\frac{1}{2}-\frac{i \sqrt{3}}{2}\right)} \, dx$

How can we force Mathematica to compute this limit? $$\lim_{x\to 1} \, \int -\frac{i \text{Li}_2\left(x-x^2\right)}{\sqrt{3} \left(x-\frac{1}{2}-\frac{i \sqrt{3}}{2}\right)} \, dx$$ It seems it ...
2
votes
2answers
130 views

Approximation of definite integral by parabolas

This question is related to Trapezoid approximation to definite integral. As promised, I am now asking about how to draw approximation of integrals by parabolas. I tried to modify MarcoB's code, and I ...
3
votes
3answers
222 views

How to Find “n” for n-th Triangular Number

For example, the 7th triangular number is 28. How do I create something that will tell me that 28 is the 7th triangular number? This is what I have created. ...
0
votes
0answers
35 views

How to express $f(x,y) = u(x,y) + i\, v(x,y)$ as $f(z)$

The $f(x,y)$ is actually a series with complex parts. I'd prefer not working this out by hand.
1
vote
1answer
50 views

Mathematica computes wrong eigenvectors? [on hold]

I have a matrix M = {{0, 0, 0, 0}, {0, 0, 0, 0}, {0, 0, 0, b}, {0, 0, -b, 0}} that I want to diagonalize. So far, I always used the following and it worked, but ...
0
votes
1answer
43 views

Functions becoming undefined when evaluated

I'm so confused I don't even know how to phrase my Question title. My function nextCol works until I use colLength, then ...

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