# All Questions

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### Numerical instabilities of a convection-(non-)diffusion equation when shrinking from a square to a triangular domain

I am trying to evaluate a parameter-dependent indefinite integral using a PDE-based scheme I described here, and I'm having some trouble when I try and cut down the domain from a square to a triangle. ...
27 views

### what's my air speed if i know these details [on hold]

What is the minimum air speed required of an F4 phantom aircraft to accelerate at 10g while pulling the nose up from a 20 degree pitch down attitude?
67 views

### How can I numerically pre-compute an indefinite integral with a parameter?

Suppose I have a function $f(t)$, and I want to compute its indefinite integral $$F(t)=\int_0^tf(\tau)\mathrm d\tau.$$ Moreover, suppose that, for any of a number of reasons, I require this integral ...
68 views

### How to solve this recursive system?

I try to solve the equation system as ...
60 views

### Notebook Magnification changes - Why?

I have written a notebook but in order to edit it, I prefer 125% magification or even 150%. I know Window>Magnification. Also there is a small symbol on the right bottom of the notebook, where I can ...
42 views

### Need Help with solve function [on hold]

I'm trying to re-write this function x = e^(-(r+(1/2)*sigma^2)*t-(g)(sigma)*sqrt(t)), as an expression of "g" instead of "x" ...
225 views

### Follow each pixel brightness in set of images (Memory constrained)

I have a set of 2700 consecutive png images (8bit, 2048*2048 pixels). I would like to visualize the intensity variation of each pixel vs. image number. Here is an example of 10 images: ...
39 views

### Possible Bug with DateObject

So my questions is going to be hard to duplicate because I am not sure when or why it happens. I've read here several bugs with DateObject, but none of them ...
55 views

### 3D orbits of moons around their respective planets

I have seen a lot of solar system models (both animated and not), but I am trying to replicate the same thing with moons. Either just one planet and its lunar system or the our whole solar system with ...
34 views

### How to run code in two notebooks simultaneously [duplicate]

I have the problem that I cannot run code in a second notebook when another notebook is being executed (here only a single core is used). The CPU of my computer has 4 cores (Win 10, Mathematica ...
70 views

### I need to write an animation of something l [on hold]

I need to write an animation of something like this: [![enter image description here][1]][1]
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### FindInstance—why doesn't it work with my expression? [on hold]

I want to find arbitrary solution of a system of equations: ...
59 views

### Split Boundary Value Problems win Algebraic Equations

Is it possible at all to solve with NDSolve (or other built in function) a split boundary value problem with algebraic equations? Please look at the following example: ...
53 views

### Product of two Meijer's Function

I want to evaluate an integral $I_1$ defined in $Eq.(1)$ as \begin{align} I_1=\int_{0}^{\infty}\frac{x\exp(-\beta x)K_1(\alpha x)}{1+x}dx\tag{1} \end{align} Where $\alpha\geq0$, $\beta\geq0$, and ...
36 views

### Shortcuts for Indentation in Text Cells?

Marking a cell's bracket and then using Alt-7 I can make it a Text cell using the formatting set forth in Default.nb or in a modification of it stored with the notebook itself (so called "private ...
61 views

### Computing quadrature points on triangle

According to http://math2.uncc.edu/~shaodeng/TEACHING/math5172/Lectures/Lect_15.PDF page 7, it is possible to compute coordinate of quadrature points by using the script ...
36 views

### Limit involving DiracDelta gives zero [on hold]

Why is the following limit zero? In[147]:= Limit[DiracDelta[ϵ], ϵ -> 0] Out[147]= 0 It does not matter if the limit is taken from either sides (+/-), since ...
39 views

### Bilinear interpolation [on hold]

I have a matrix with n rows and m columns. I would build a two-variables function which interpolates these points (it's a bilinear interpolation problem). How can I found a two variables function ...
32 views

### Problems in animating graphs and its extrema

I tested to animate 2D graph and its extrema for simple case using Mathematica. ...
71 views

### Calculating products of given length of two matrices

I have the following problem to solve. Let us have two given square matrices $A$ and $B$ of the same size and a positive integer $n$. I would like to produce all products of length at most $n$ of ...
67 views

### RandomPoint fails with a large enough number of points

Bug introduced in 10.2.0 and fixed in 10.3.1. RandomPoint is new in 10.2.0. I have defined a simple ellipsoidal parametric region: ...
46 views

### Force mathematica to consider variables as real [on hold]

I want to implement an optimization of the form: NMinimize[{function,{constraints:A1^2+A2^2+A3^2+A4^2 ==1}},{A1, A2, A3, A4}] where I want to tell mathematica ...
21 views

### Custom configuration of kernels in Mathematica for multiple remote hosts

Yesterday I succeeded in getting a remote kernel working on a remote Linux machine. Now since the method I use gets me to initiate kernels manually, I was wondering if I could start kernels on two or ...
33 views

### How can I get a list of the “coefficients” of Quaternion[1, 2, 3, 4]? [duplicate]

I want to input: Quaternion[1, 2, 3, 4] to get a list: {1,2,3,4}.
72 views

### Use of some functions of the Developer Utility Package, such as BesselSimplify

The Developer Utilities Package contains several functions that look interesting: BesselSimplify GammaSimplify ...
51 views

### How can I convert a 3D contour plot into a region for use as a custom slice in ListSliceDensityPlot3D?

The documentation for ListSliceDensityPlot3D says ListSliceDensityPlot3D[{{x1,y1,z1,f1},{x2,y2,z2,f2},…},surf] generates a ...
30 views

### Hidden assumption in Mathematica integration [duplicate]

If I do Integrate[Exp[I*omega*t],t], it gives me $\frac{1}{\omega} e^{i \omega t}$, as expected in most of the cases, except when $\omega$ is 0. Mathematica seems ...
42 views

### Shared variable can not be distributed again after UnsetShared

I see a weired behavior in my MM 10.3 version. Can someone reproduce it or explain what is going on? The code is easy: ...
19 views

### Solving a simple ODE [duplicate]

I am trying to solve $y(x)' = \sqrt{y(x)}$ with initial condition $y(0)=0$ for $x\in \mathbb{R}$. I have tried this: DSolve[{y'[x] == Sqrt[y[x]], y[0] == 0}, y[x], x] but this gives {{y[x] -> ...
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### Popup window shows after kernel closed when using J/Link

A popup window always show after kernelLink.close(); And this only happen after expression evaluated as graph. Such as ...
74 views

### A simple question about replaceall and plotting

I was trying to replicate the picture produced on the following Wikipedia page: https://en.wikipedia.org/wiki/Evolute with the astroid emerging as the envelope of normals to the ellipse. I ran into ...
47 views

### Riemann Zeta function definition was expanded by Euler with an infinite product series [duplicate]

The Euler infinite product series definition for Riemann's zeta function requires that Mathematica use all prime numbers in the product series. Can anyone help me with the code that will give a ...
32 views

### Substitute arguments before evaluating variables in Block [duplicate]

Suppose I have f = x^2; mod[x_] := Module[{}, f] Then mod[3] returns x^2. Is there any way to tell Mathematica to treat the "x" inside of f as the same "x" as ...
231 views

### why MatchQ is fast and Replace slow?

Consider a large expression, say a polynomial with 25 terms expr=Product[Unique["a"],{i,1,25}]; to which you apply the following replacement rule: ...
40 views

### How to set Ticks for an AngularGauge?

How do you set custom ticks on an AngularGauge. ...
93 views

### Color a single contour from a ListContourPlot3D using values from a list

I want to map an electrostatic potential onto a density map. How can I color a single contour from a ListContourPlot3D using the values from another list? Make ...
38 views

### Plotting a function based on complicated integral

I have this function : f[Lambda_] := K Integrate[x Exp[- x^2-Lambda x] HypergeometricU[-Lambda,1/2,(x+ Lambda/2+2)^2],{x,0,Infinity}]; where ...
34 views

### Coding help on plotting two functions [on hold]

I am trying to plot two functions. Trying hard, but not able to see what is wrong in the function definitions. ...
237 views

### Rotating an Interpolating Function

I have used the following code to generate eigenfunctions of a PDE: ...
21 views

### N[variable,2] displays 6 digits [duplicate]

The following code doesn't behave as I expect. Rather than getting 2 digits upon varying r, I get the default value of 6 digits. What's up? ...
104 views

### Out of range red glow on inter-dependant sliders in manipulate

In manipulate, I need to define two sliders : one basic slider, and a second one for which the end value depends on the current value selected on the first slider. How can I achieve this in ...
227 views

### Combinations of multiple matching patterns

I wonder if there is any nice way to combine DownValues (or any other suitable rule-/pattern-/function -based Mathematica construct) when multiple patterns match an expression. Let me explain what I ...
103 views

### Efficiently generating tuples with Outer

I'm trying to efficiently generate tuples of lists of objects that satisfy a given criterion. The similar questions that I have found on this website end up finding a specific workaround for the given ...
41 views

### using Map to apply 2 lists to the LCM function - help [duplicate]

I have 2 lists of numbers and I want to quickly compute the array of answers to the LCM function for the 2 lists and a 3rd static number. I tried the following ...
29 views

### How to simplify a ratio [on hold]

I have a ration of the form $\frac{p^2}{(p^2+1)^2}$. I can simplify it using $p^2=p^2+1-1$, and to get $\frac{p^2}{(p^2+1)^2}=\frac{1}{p^2+1}-\frac{1}{(p^2+1)^2}$. How can I create the rule to do it ...
69 views

### Euler-Maclaurin summation

I want to compute asymptotic approximations to partial sum of harmonic series in Mathematica, using Euler-Maclaurin summation formula. ...
33 views

### Reverse element in nested list [on hold]

Suppose I have a list as the following: list={{1,9},{7,0},{8,6}....} How can I reverse the element in such way that the output would be the following: ...
26 views

### Unstable command line startup time [on hold]

I installed Mathematica in an Ubuntu machine, and the start up time in command line is very unstable. Some times open instantly, another times get 40 seconds to open it. I'm using no interface, just ...