All Questions

0
votes
0answers
13 views

Understanding Transpose, dot and at

I found this formula Transpose[{Tv1, Tv2}].Inverse@Transpose@{v1, v2}.{x, y} in some post but lost the link. Now I need to understand why this formula solve my ...
0
votes
0answers
11 views

How reproduce old SplineFit function?

Prior to version 8, Mathematica included a SplineFit function that could be used, for example, in the form: ...
1
vote
1answer
8 views

How can empty fields in a csv file be set to Missing when importing as a Dataset?

When importing a csv file with empty fields as a Dataset, the empty fields are set to zero-length strings (""). There is an option, ...
1
vote
2answers
15 views

How to visualize indifference curve in a 2D plot?

I have two functions f(x,y) and g(x,y). I wish to perform two tasks on a 2-dimensional figure: (1) plot the curve where each point satisfies f(x,y)=g(x,y) (2) mark one side of the curve with red ...
0
votes
1answer
14 views

running a loop to check for multiple congruences

I have the code for a loop to run. Right now it can check if a number is a square and at the same time check if it is congruent 0 mod 47. My questions is, how can I alter the code to see if it is ...
0
votes
0answers
22 views

Can NDSolve be used to model gravitational motion due to an ellipsoid?

I'm trying to use Mathematica to get a numerical estimate and plot of the motion of a point mass in the gravitational field of a fixed, non-rotating ellipsoid. Ideally, I'd like to plot the motion ...
0
votes
0answers
15 views

Impose conditions on PDF distribution

Consider some data data = {{x1,y1},{x2,y2},...} I organize a density distribution using ...
1
vote
1answer
31 views

Why do I get different symbols (a) with the same FontFace (Cambria Math)?

When I create an equation in MS Office, it uses Cambria Math, and I get the following when I use variable 'a'. When I try to use Mathematica to create graphics for my files, I can try to use ...
5
votes
1answer
73 views

ContourPlot — How do I color by contour curvature?

I'm plotting the stream lines of fluid flow past a cylinder, and I would like the colors to increase with contour curvature (i.e. increase as the velocity of the flow increases. Here's a MWE that ...
2
votes
1answer
26 views

Element-wise multiplication of matrices with different dimension

I am interested in efficient element-wise multiplication of matrices with different dimension. Here is my solution: Matrix 1 with dim = {3, 4, 4} ...
2
votes
0answers
37 views

Simplifying long expressions leads to memory allocation failure

I am currently trying to manipulate a number of expressions into a particular form that will allow me to determine their poles and zeros: ...
0
votes
0answers
38 views

Random integers [on hold]

I'm wondering if there is any way to generate 10 random integers (between 1 and 10) in a way where once an integer is selected, it does not get selected again. I've tried using RandomInteger and then ...
2
votes
1answer
27 views

Incorporating Signature with Permute for symmetric groups

Let $$f(x_1, x_2, x_3, x_4) := \frac{x_1^{-3} x_2^{-2} x_3^{-1}}{(1 - x_1^2) (1 -x_1^2 x_2^2) (1 - x_1^2 x_2^2 x_3^2) (1 - x_1^2 x_2^2 x_3^2 x_4^2)}.$$ I am trying to compute $$\sum_{w\in S_4} (-1)^{\...
1
vote
1answer
35 views

Rearranging similar terms in an equation

In a piece of code I am writing, I run into an equation of the form ...
0
votes
0answers
45 views

Displaying equations in a slide show

I'm trying to make a slide show with Mathematica, and the equations are being written in a pretty nasty looking font. I click the Display Equation environment, but the equations still look pretty ...
0
votes
1answer
39 views

How to do a fit on multiple peak with a voigt function

I looked a lot on the other questions to do that but I can't find a way to do it properly. So here is my question. I have a spectrum of OH and I would like to do a voigt fit on every peak it has to be ...
0
votes
0answers
28 views

Creating lists of values referring to the same index

I would like to code lists of the form: Ai = {x0, x1, x2, x3, ...} Bi = {y0, y1, y2, y3, ...} where the index i refers to the elements 0,1,2,3, etc., across all lists that I make. The values in the ...
3
votes
3answers
64 views

Changing the position of rows and columns in a matrix

I have the following self-explanatory question. https://1drv.ms/u/s!AsyHs3E_aioxhipb3wSPSX_heN-t As seen from the above matrices, I start with the "original" ...
3
votes
2answers
144 views

Determining multivariate least squares with constraint

I have some composition data for a geological sample and its constituent minerals. I want to estimate the proportions of the minerals that make up the bulk sample. This is essentially a mass balance ...
0
votes
0answers
38 views

NDSolve with Finite Element ignoring terms in partial differential equations?

Solving a 1D dispersive wave equation with NDSolve and the finite element method seems to give completely wrong results. Consider the 1D PDE below ...
1
vote
1answer
27 views

How to organize the 2D data into binned distribution?

Consider a data data = {{x1,y1},{x2,y2},...} with n rows. I want it to be organized into $n$ bins for $x$ and $m$ bins for y, with the positions $x_{i}, x_{i+1}$...
0
votes
0answers
23 views

Missing value analysis, an advanced work with missing data

Does Wolfram or any package contain procedures for statistical work with missing data? Not just something as "remove Missing and compute with remains" I am asking ...
0
votes
0answers
36 views

Taylor expansion in Quantum

Recently I am trying to use Mathematica to compute a Taylor expansion. My function to expand is this" $$\begin{aligned} &\exp\Big(-i(\frac{h+\delta h}{2}\sigma_x+\frac{J+\delta J}{2}\sigma_z)\...
0
votes
1answer
21 views

Multiple collection of terms

As the title suggests, I am interested in how to perform multiple collection of terms. This means that for a given expression a*x*b + c*x^2*d+a*x*k, I want to ...
0
votes
0answers
16 views

Ordinal subset in the set of classes

I need to do an unusual classification, which I probably will not achieve only with Classify[]. Features are quite simple vectors composed of numbers and nominal ...
1
vote
2answers
42 views

Simplify differential expressions

One can differentiate a two dimensional vector like this, ClearAll["Global`*"] u[x_, y_] := {f[x, y], g[x, y]} Div[u[x, y], {x, y}] with output ...
3
votes
3answers
86 views

Adjusting bounding box of PlotLegends in TimelinePlot

I'd like to align the elements of the PlotLegend in a single horizontal row beneath the TimelinePlot, as there is plenty of room ...
2
votes
1answer
65 views
0
votes
0answers
32 views

Plotting dispersion relation [on hold]

Why is the second funtion dos not appear in the graph ? ...
0
votes
0answers
45 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 ...
2
votes
1answer
57 views

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

I have an exercise looking like this: Analyze the integral $4\int_{0}^{1} \sqrt{1-x^2} \, \mathrm{d} x$ numerically by deviding the interval ${]0,1[}$ into three equal parts, then summarize the ...
6
votes
4answers
336 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
52 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
2answers
44 views

How to define multivariable vector funtion? [on hold]

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]} ...
0
votes
2answers
44 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
37 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
30 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
31 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
2answers
90 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
33 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
287 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
68 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
156 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: ...
2
votes
1answer
66 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
26 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 ...
3
votes
2answers
73 views

Delete duplicates in tuples

I use the following code to create a list of input parameters: ...
0
votes
0answers
43 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
60 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,...
4
votes
1answer
57 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
26 views

Selecting specific elements of a list

Suppose we have the following list: ...

15 30 50 per page