All Questions

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 ...
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 ...
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
120 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....
4
votes
2answers
40 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
36 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
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
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
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 ...
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: ...
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 ...
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 ...
5
votes
2answers
201 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: ...
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....
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: ...
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. ...
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 ...
2
votes
2answers
43 views

Delete duplicates in tuples

I use the following code to create a list of input parameters: ...
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, ...
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,...
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
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 ...
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?
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 ...
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 <...
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 ...
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, ...
-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 ...
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
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: <...
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 ...
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
0answers
23 views

Convincing Reduce[] to work

The following should return True: Reduce[ForAll[{t, x}, x > 0, Exists[y, x^t == y]],Reals] but ...
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 ...
0
votes
0answers
13 views

numpy.linalg.solve returns a solution for a matrix that is not full rank [migrated]

I've been learning the basics of OLS regression, and was told that there can't be perfect multicolinearity in the model. I have a matrix that is obviously not of full rank: ...
0
votes
0answers
21 views

Limiting value problem with Plot3D [on hold]

When running this code ...
1
vote
0answers
18 views

Moving to the last placeholder with inputautoreplacements

I have had a long-standing problem when I try to use my inputautoreplacements in a text cell. The replacements I have made include boxes that include placeholders. When in the text cell, you type ...
0
votes
1answer
74 views

Second Derivative in MMA

I would like to ask, why the following second derivative is wrong in MMA ...
1
vote
0answers
40 views

how to linearize an equation? [migrated]

How does one linearize this equation?
2
votes
2answers
41 views

DisplayForm problem with pi in FractionBox

The following line produces an output with the text "Pi" displayed instead of the symbol for pi. All help with an alternative or correction of this would be much appreciated, thank you.
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 ...
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, ...
4
votes
1answer
124 views

Imaginary part of expression too difficult to calculate

I am trying to calculate the imaginary part of a long expression. It's a long enough expression that Mathematica "hangs" when you run: ...
0
votes
0answers
29 views

Why OpenerView reduces the size of my equation

In this code the equation comes out with the right size. ...
0
votes
0answers
28 views

Having difficulties using results returned by Solve

I'm new to Mathematica, and I am still having some issues figuring out the general syntax. I've got to use Mathematica, as my research requires a powerful symbolic math program. I'm having trouble ...
2
votes
1answer
29 views

How can I crop a 3D object in the format .obj or .noff?

bunny= Import[ "http://exampledata.wolfram.com/bunny.noff.gz" ] How can I crop this .noff object to get something similar to the attached photo? The 2nd image has 30% cropped and the last image has ...
0
votes
0answers
37 views

How do dereference part of a dataset? [on hold]

I have a certain function that is returning data in curly brackets instead of a direct value. How I extract the value so that I can use it?

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