All Questions

6
votes
3answers
1k views

How can I invert a Laplace transform numerically?

I have a very complicated expression, which I want to transform using the inverse Laplace transform. The built-in function InverseLaplaceTransform doesn't work. So,...
2
votes
1answer
66 views

Help in advection-dispersion equation using NDSolveValue

i have the advection-dispersion equation: Dz = 0.0000738739; as = 2.21622*10^-6; Dz*D[u[z, t], z, z] - as*D[u[z, t], z] == D[u[z, t], t] The boundary and ...
1
vote
1answer
46 views

System of coupled differential equations

I am trying to solve the following system of equations, but I get as the output the command itself. ...
1
vote
1answer
29 views

How to create dynamic PlotLegends?

How to add dynamic PlotLegends to the below code? ...
0
votes
0answers
30 views

Using Dynamic[] function

I would like to use Dynamic[] to print progress of evaluation of some function, which works quite long. let's say that the definition of ...
-2
votes
0answers
40 views

Mathematica problems [on hold]

What means when this message in mathematica program Factor[Solve[E3 == 0, b2]]={}, such that in the expression of E3 there is b2.
1
vote
0answers
25 views

Keyed Hash for HMAC SHA256

I'm trying to use AWS REST API's (because I can't rely on AWSLink`). The sample C# code from Amazon uses this a lot: ...
2
votes
1answer
180 views

DotPlot for prime numbers

I was thinking to use a dotplot to give a description of prime numbers. On Wolfram website there is written that each dotplot can be built by ...
1
vote
1answer
92 views

Inverting the order of a Table - Prime numbers

In a previous post I asked for the possibility to have a binary image of the coprimality inside the natural numbers. The following code ...
-1
votes
1answer
138 views

Plot Ramanujan Primes

I often investigate on Ramanujan primes. Is it possible to apply this procedure described in DotPlot for prime numbers ? I think so but which is the condition I should use? I am trying from several ...
3
votes
3answers
110 views
+50

Another difficult background subtraction

I'm trying to remove the background but it is removing part of the bag in the foreground (because it is white too): Here's what I've tried: ...
3
votes
1answer
43 views

VoronoiMesh with custom distance function

I'm failing at reading the documentation. Is there a way to specify the distance function used by VoronoiMesh? As a stripped down example say I have a rank-1 lattice such as: ...
1
vote
1answer
38 views

How do I divide an integral into parts and sum the total?

I have an exercise looking like this: Analyze the integral $4\int_{0}^{1} \sqrt{1-x^2}\ \tex$ numerically by ng the interval (2,1) into three equal parts, then summarize the integral parts. I just ...
6
votes
3answers
148 views

Taking the numerator and the denominator

Is there any way to get the Numerator and the Denominator of an expression split in the same way that Mathematica graphically represents it. Say I have an expression: ...
0
votes
0answers
39 views

Issues solving system of differential equations [on hold]

d = NDSolve [{x''[t] == (x [t] + a[t])/(-2), a''[t] == -x''[t]/2, x[0] == 0, x'[0] == 1, a[0] == 0, a'[0] == 0}, {x, y}, {t, 20}] Keeps returning the error "To ...
4
votes
2answers
39 views

Identifying total derivatives

I would like to identify which terms in my expression are a total derivative and which ones are not. For expressions in which all terms are a total derivative, one can simply use integrate to find ...
1
vote
3answers
35 views

How to define multivariable vector funtion?

I would like to define a function of variables having two components as $u(x,y) = (f(x,y),g(x,y))$. I defined such a function as u[x_, y_] := {f[x, y], g[x, y]} ...
1
vote
0answers
13 views

Utilisation of Processors across multiple cpu sockets not 100%, limited to a single cpu socket

I have a CPU with 32 Physical Cores, 64 Virtual Cores across two physical sockets. It is E5-2686 v4 intel. There are a few issues. 1. Mathematica only sees 16 Physical processors when checking $...
6
votes
4answers
118 views

Sort with assumptions

I have a list which looks like this list = {0, Subscript[x,7], -Subscript[x,3]-Subscript[x,9], -Subscript[x,9]}; and all the $x_i$'s are positive semidefinite (i....
2
votes
3answers
59 views

Divide a list into two lists with equal sums

I have a list with L elements. I want to find an index within the list, that divides the list to two separate lists so the sum of elements in each of them are equal....
5
votes
2answers
200 views

Derivative of an interpolated function

I am trying to take the derivative of an interpolated function. I am given the function values and the derivatives at some irregular points. Here is my minimal working example to reproduce the error: ...
1
vote
1answer
38 views

How to show the answer in terms of another variable

if we have A = 1; B = 44 + 1 output :: B = 45 how we can show B like this output :: B = 44 + A
1
vote
1answer
39 views

Can pattern assumptions be made reliable?

It is possible to use patterns in assumptions such as f[_]>0. This does not seem to be explained in the documentation but is for instance pointed out in Is it ...
7
votes
1answer
155 views

How to add solutions from potential flow calculations (including circulation)?

Now we have the finite element method how do you combine potential functions appropriately? A classic problem is to calculate the lift on an aerofoil by adding circulation to a potential flow ...
1
vote
0answers
27 views

How do I Select when the key of an association is a multi-word string

I have imported some survey responses into a Dataset. I now want to select those rows where the response to "participant type" == "Virtual". I discovered that this ...
0
votes
2answers
49 views

How to force simplify to drop common denominator in inequalities?

Simplify[c>0 && a/c <= b/c] results in c > 0 && a <= b, as hoped. However when ...
1
vote
2answers
58 views

How to plot this set $M\subset\mathbb{R}^3$?

Is there a way to plot the following set with Mathematica? $M=\left\{ \left(x,y,z\right)\mid x\in\mathbb{R}\:,\:y=\left|x\right|\:,\:0\leq y<z\right\}$ I think it's suppose to look something like ...
-1
votes
1answer
57 views

Liquefying of Nitrogen & Oxygen Gaseous to Liquid Phase. Thermodynamics. How to plot solution? Solved

Process of Liquefying of air composed of 79% Nitrogen & 21% Oxygen from Gaseous to Liquid Phases as Follows: 1) When Temperature is higher than T>83 k they both are gas. 2) at T=83 k and less ...
0
votes
0answers
30 views

Changing speeds of orbiting bodies with Manipulate

The code below is attempting to simulate the orbits of Earth and Mars along with a Hohmann transfer orbit. Since each one of these bodies orbit at different speeds, I need a way to specify each orbit ...
1
vote
1answer
30 views

Replacing with Elements from a List [duplicate]

I have a fairly complicated expression with nested lists and I want to substitute a given string for each integer. Here's a simple example where ind is my integer-valued data structure and names is ...
2
votes
2answers
43 views

Delete duplicates in tuples

I use the following code to create a list of input parameters: ...
2
votes
2answers
45 views

Identifying points in the frontier of a set

Let me start with an example. Let $$\mathbf{A}=\begin{bmatrix}3&1\\2&3\\1&5\end{bmatrix},$$ and let $Q=\{\mathbf{q}\vert\mathbf{q}\in\Bbb R^3_+ \land \sum_i^n q_i=1\}$ and $\alpha=(.5,.5,...
7
votes
1answer
483 views

Fashion segmentation with a neural net?

I would like to train a network that can parse clothing: Does anyone know of a fashion segmentation network with or without pre-trained weights available that I can use in Mathematica? Update: I ...
-1
votes
0answers
36 views

`DistributionFitTest` for 2D data [on hold]

How can I make DistributionFitTest accept 2D data? According to the Documentation - it should be able to accept multivariate data, and the test distribution can be ...
0
votes
0answers
22 views

Monitoring PolynomialReduce/Alternatives for other CAS packages

I have a large generic polynomial That looks like $N = \sum_{i_1,i_2\cdots}c_{i_1,i_2,i_3,\cdots} {x_{1}}^{i_1}{x_{2}}^{i_2}\cdots $ This could have anywhere between 3000-9000 terms with a maximum ...
0
votes
0answers
39 views

How do I uninstall an old version of Mathematica?

My SSD is getting full, and while trying to clean it up, I found one of the largest things on here is an installation of Mathematica 10.3. As this is an outdated version, I would like to remove it, ...
1
vote
1answer
24 views

How do I plot a function that contains variables I have previously defined?

I am trying to plot t as a function of the variable EE which is itself included in variables I have defined. However, when I ...
1
vote
1answer
24 views

Selecting specific elements of a list

Suppose we have the following list: ...
-1
votes
0answers
30 views

How to force Mathematica not to show the result in numerical format [on hold]

I have a function f[x_] = 4/3 x. However, Mathematica displays it as 1.3333 x. How to force it to display the function in the form 4/3 x?
7
votes
1answer
96 views

Strange behavior of Out[]

Let's create two notebooks external.nb and primary.nb. Then call the external.nb notebook from the primary.nb and investigate values of Out[ ]. The context of the external notebook is not important, ...
2
votes
1answer
23 views

Discretize Graphics3D with Scale and Rotate?

How can I discretize a Graphics3D object that makes use of Scale and Rotate? When I try <...
15
votes
3answers
1k views

Isometric perspective for Graphics3D

Is it possible to render Graphics3D in an isometric projection? I know that the ViewPoint option can be used for orthogonal ...
1
vote
1answer
35 views

How to compute delta coefficients in mathematica

I want to get delta coefficients calculated. The definition can be found here. However, I don't know what to do with the minus indices. I have tried computing it in a slightly different way, namely: <...
1
vote
1answer
75 views

Conditional evaluation: black hole cross section

I'm trying to calculate the collision cross section of black holes, more precisely, I want the critical impact parameter $b_{\text{crit}}$ for a given initial velocity $v$ such that, at this speed, ...
0
votes
1answer
44 views

Update initial conditions recursively/sequentially within ParallelTable using NDSolve

I am modelling 3D motion of particles inside a force-field using second-order coupled PDEs, which I solve from time t=t0 to t=t1 with initial conditions x0,y0,z0. I have a total number of "particles" ...
6
votes
1answer
48 views

Workbench documentation build fails

My old installation of Workbench went inexplicably wrong, so I tried a fresh install of Eclipse & Workbench. Looks good until I try Documentation Build, when I get the following error: An ...
2
votes
2answers
48 views

Finding the amplitude of function solved using ParametricNDSolve

I have been trying to find the peaks of a function I have plotted using ParametricNDSolve. I have to find these peaks to calculate the amplitude of all the various waves in the observed output. By ...
2
votes
0answers
35 views

How to automatically transform Abs[Cos[x]]Sec[x] to Sign[Cos[x]]?

Out of some simplification, the term Abs[Cos[x]]Sec[x] appears. How can I make the code automatically transform ...
0
votes
1answer
74 views

Second Derivative in MMA

I would like to ask, why the following second derivative is wrong in MMA ...
3
votes
2answers
173 views

The multiplication of list of matrices

I need to multiply 3 lists of matrices (b.a.b) as the following code ...

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