# All Questions

21 views

### MatrixExp[] of a complex matrix of size about 10000 by 10000

I used the MatrixExp[] of a numerical complex matrix of size about 10000 by 10000, and I ...
12 views

### Differentiation inside pakage

I am trying to put all my functions in a single package and some of them do not work because of differentiation. Suppose I have the following package ...
10 views

### Trying to find parameters for a system of ODEs

So I have a system of 4-dimensional system of ODEs and I'm trying to find any values of parameters that satisfy properties I need. In this picture, I want two basins of attraction, one of which the ...
26 views

### Colors on a 3D curve not working

I'm having troubles applying colors to a simple 3D curve plot. Here's the code : ...
40 views

### I keep writing functions like this one: subtract[{a_, b_}] := Subtract[a, b] [duplicate]

(Edited to provide an example) Recently I have found myself writing silly functions like the following, which is just a new arity of Subtract in which the arguments are inside a list. ...
21 views

### Real time solution of a DE with changing parameters

I have a set of coupled differential equations (9 equations with 9 unknowns) and 9 known initial conditions to describe the motion of a quadcopter. Question: how can I make a real-time simulator out ...
21 views

### Associations - getting values according to a key pattern

I want to get all counts of trigrams that with "th" (or any other given digram). ...
15 views

### Selecting the parallel kernels where tasks can be executed

When I use ParallelSubmit, is it possible to select on which kernel a task can possibly be executed ? For example if have 3 parallel kernels, can I only use 2 of them so that one is remaining in case ...
16 views

### How to import a Graphs & Networks graph as a Mathematica graph?

This graph (as a picture) is given below: I am wondering rather than setting up this network graph using Mathematica syntax such as PathGraph,...
31 views

### Gradient Help w/ Problem 1 [on hold]

​Go with f[x, y, z] = Log[3 x^2 + y^2 + z^2] In which direction should you leave the point {2.1, -3.7, 4.3} to get the ...
25 views

### How to define a number of infix operators with predefined relative precedences

Reading a number of questions about infix operator notations I want to ask if somebody could reimplement the problem below in a simpler way, say modifying ...
16 views

### Custom drop-down list of tags for Dataset Keys similar to CountryData

CountryData produces a drop-down list of tags when you enter a string. I would like to replicate this functionality for a ...
43 views

### thickness of plotting edges

used these codes to might a simple triangle, which nodes have different effects each other: ...
37 views

### Solving matrix optimization

I have the following problem. Let $X_1, X_2, \cdots, X_k$ are $n \times n$ Hermitian matrices (need not be positive) given. Let a $n \times n$ positive matrix $A$ is given such that $Tr(A.X_j)<0$ ...
77 views

### How to get the desired (equivalent) answer from Integrate?

This is the integrand: 1/beta/(2*z)/(1 - beta) // TraditionalForm Integrating with respect to z, gives ...
77 views

### Displaying a list of percentage values according to their classification

I have a list of percentages as follows: percent = {21.15, 42.3, 57.68, 73.06, 84.6, 90.37, 96.14, 99.99, 99.99, 99.99, 99.99} I want to classify these ...
39 views

### “Part specification is longer than depth” warning in Position function [duplicate]

I'm working on a project which analyzes financial data. I download the price and dividend information for the SPY ETF which tracks the S&P 500: ...
45 views

### Numerical integration with assumptions

I have to numerically integrate an integral with two variables r and v, but I want to do the evaluation assuming ...
60 views

### Program to demonstrate rotation according to quaternion values

On the Wolfram|Alpha website, I type quaternion(1,1,1,1) into the search field. Wolfram|Alpha shows a 3D transformation of the quaternion values representing the orientation of an object. I have 9 ...
51 views

### Mathematica requirements management [on hold]

Is there a way to use Mathematica notebook as a requirements document as it's possible in IBM DOORS ? ...
57 views

### How to find points along the inner and outer edge of a ring along a specific direction

I have a set of random numbers distributed on a annular disk. I want to find points on the inner and outer edge along a particular angle. One possibility is to use ...
39 views

### Why can not the vector be transposed in integrating over a region? [duplicate]

Clear[x, A]; A = {{2, -1, 0}, {-1, 2, -1}, {0, -1, 1}}; Integrate[Exp[-x.A.{x}\[Transpose]/2], x \[Element] FullRegion[3]] This code raises an error ...
17 views

### Page breaks and headings in long table or grid

I have a need for long tables in a document I am producing but I am having difficulty. The printed document ends up with page breaks midway through the table which cuts rows part way through. I'd also ...
101 views

### intermediate steps of a Mathematica operation

How to make a multiplication or division, the intermediate steps. The numbers can be rational - decimals? it seems the OP merely wants Mathematica to show him how to multiply and divide the way ...
85 views

### Equality of Reciprocal with Negative Exponent

I want MMA to tell me if two, rather large, expressions are equal. My minimum working example follows. I want MMA to tell me that the following is true:$$x^n = \left(\frac{1}{x}\right)^{-n}$$ I have ...
42 views

### How to get an element mesh from a region?

I've been exploring a new 3D solid commonly called the "Chestahedron" (7 faces of equal area). I wanted to find the centroid, so turned to Mathematica and found it!:) Other things of interest turned ...
65 views

### Clean & efficient bounding box non-intersection test

I would like a quick test to tell me that segments $ab$ and $cd$ cannot intersect in the plane. If the maximum $x$-coordinate of $a$ and $b$ is less than the minimum $x$-coordinate of $c$ and $d$, ...
237 views

### Redefining a built-in operator

Is there a way I can redefine the || operator such that a||b will be 1/(1/a + 1/b)? Is it ...
35 views

### Once working code fails upon restarting Mathematica [on hold]

I had a code which worked flawlessly, then upon shutting down mathematica and re-starting it, the code failed with the following error message: "The function value -Abs[f[0.0228659,I/6]] is not a ...
29 views

### choosing the number of points in FindFit function [on hold]

I am trying to find the best function to fit a set of data as following, ...
11 views

### Probability Quesiton Help [on hold]

I am working on some exercise questions from probability. I am stuck at this question. Can somebody help me to solve this. I would really appreciate. In a certain country, 35 percent of people are ...
4 views

### How to write this Google docs, percentage calculation function? [migrated]

I track my diet (macros) in Google docs. For 1 day my protein is 114.63 carbs 194.75 and fat ...
37 views

### Hook Length Formula and Ferrer's Diagram

So, I am new to using Mathematica, and trying to write some code that needs to use hook length of each cell in Ferrer's diagram of a partition. I first thought of using for loops to manually count ...
50 views

### How to simulate a homogeneous nucleation? [on hold]

From this topic, Animating a Voronoi Diagram, I can simulate heterogeneous nucleation. Based on Voronoi diagrams, how can I use Mathematica to simulate homogeneous nucleation?
57 views

### I want a mix matrix [on hold]

I have a matrix with dimensions m x n and elements f[p, q] and another matrix with dimensions i x j and elements g[r, s]. How ...
62 views

### Fixing “incompatible shapes” when multiplying arrays [duplicate]

A part of my notebook returns to me the following expression: ...
40 views

### Is there a way to pre-calculate a slow animation and then run easily with no lag? [duplicate]

I have an animation of a triple pendulum on a moving base, however even after trying to change the whole coding to make it faster by using module and all it is still pretty bad as I need it to be ...
92 views

### code is ignoring WhenEvent

I would like the value of x[t] to be equal to 0 when it has a negative value so I used WhenEvent but it has no effect on my code ...
141 views

### Global context not empty at startup in v10.2.0

Bug introduced in 10.2 and persisting through 10.2 or later Note that the analysis of this problem revealed a different problem than in Potential pollution of Global context in fresh kernel (see ...
60 views

### Labeling columns in grouped charts separately

I want to label sequentially some charts. Say, for instance, that I had: ...
93 views

### GeoProjection for astronomical data - wrong ticks

Here is an excellent answer to what I wanted to do, and it works like a charm. Unfortunately, when I want to change it a bit, it fails. For setting the stage, here is the datafile, and this is my ...
70 views

### Error in the solving of the simultaneous Ordinary Differential Equation [on hold]

As I am trying to get the solution of the simultaneous ordinary differential equations ...
45 views

### Funny behavior when computing dot product of coefficients with high-order polynomials

I have a similar problem to Funny behaviour when plotting a polynomial of high degree and large coefficients. However, the thing being evaluated is not just a polynomial but a dot product of some ...
131 views

### Difficulty using LUDecomposition

I'm having trouble using LUDecomposition with pivoting. I read the Mathematica help on this particular command, but I'm still lost. Take a matrix like: ...
162 views

### Why is mathematica eating a row from QRDecompostion

I'm attempting to calculate the QRDecomposition of the matrix: a= {{1,3},{0,5},{2,-8}} QRDecomposition [a] The answer mathematica gives me is: - Q which is a ...
111 views

### Help with Integration

I am new to Mathematica, and I need help with integration of the following Reliability expression (from a well-known Reliability Model). $$R(t)=e^{-Ne^{-bt_i}(1-e^{-bt})}, t \geq 0$$ I have ...
17 views

### How to disable OperatorSubstitution in a style sheet without losing syntax highlighting for local variables

I'm trying to define a custom style sheet that has "OperatorSubstitution" set to false in order to keep fonts consistent. However, whenever I disable this, I lose ...
51 views

### Derivative of vector dot product with respect to a vector

I have the expression: Transpose[gvecI, {2, 1}].x (m[1] + m[2]) gvecI and x are [3x1] ...