2
votes
1answer
147 views

how to calculate the covariance of sample central moments

$\bar{x}= \sum_{i=1} ^{n} \frac{1}{n}x_{i}$ $m_1=\sum _{i=1} ^{n} \frac{1}{n} (x_{i}-\bar{x})$ $m_2=\sum _{i=1} ^{n} \frac{1}{n} (x_{i}-\bar{x})^2 $ $m_3=\sum _{i=1} ^{n} ...
0
votes
1answer
254 views

How To Use D[ ] to Define a System of PDEs

We have two variables $u_{1}$ and $u_{2}$ which are functions of $x,t$. That is, $u_{1}=u_{1}(x,t)$ and $u_{2}=u_{2}(x,t)$. Consider the the system of partial differential equations $$\frac{\partial ...
1
vote
1answer
42 views

Out labels looks strange after turning on magnification

As everything in Mathematica looks too small to me, so I turned on magnification when I am working. It looks good on windows: However, the Out tag is dislocated ...
2
votes
0answers
52 views

Import names into notebook namespace [duplicate]

I have function that at some point has list of strings (e.g. {"apple","pear"}) and I want to declare (initialize) those variables in notebook namespace to default ...
4
votes
1answer
164 views

Arrowheads in VectorStyle and StreamStyle doesn't work properly in VectorPlot and StreamPlot, respectively. A bug?

I'm using Mathematica 10.0.2 for Mac. Arrowheads given in VectorStyle for VectorPlot ...
6
votes
1answer
128 views

Graphics3D and Bit Depth of Rendering

A year or so ago, I sent this question to WRI (nb- a former employer of mine) and, as happens with bug-reports-that-arent-bug-reports, it was swallowed into the black hole that is Chambanna. So- I ...
1
vote
1answer
102 views

Finding adjacency matrix of a Mathematica's in-built graph? [closed]

I want to get the adjacency matrix of an in-built graph, say the dodecahedral graph. Naively using AdjacencyMatrix[Dodecahedral] doesn't give it to me. Any ...
4
votes
0answers
154 views

Possible Mathematica Bug? Blank Screen

I'm a student using Mathematica on a 2012 macbook pro with OS X Yosemite. Mathematica was running fine on my computer for a long time - one day, seemingly randomly, a blank screen started appearing ...
1
vote
0answers
40 views

Does “FiniteRingData” or something like that exists?

I want to find a function like FiniteGroupData but for finite rings. Does something like that exists?
2
votes
4answers
132 views

Pairs of data to Classify[]

Suppose I had the following data a={1,2,3,4,5} How would I turn this into b={{1,2,3}->4,{2,3,4}->5} That is, ...
1
vote
1answer
2k views

Add assumptions to Solve command

I want Mathematica to solve the following by assuming the part within the Log function, which is ...
5
votes
2answers
141 views

How can I run a list of Tasks serially?

I have a list of ScheduledTask's to run in sequence one at a time. How can I set these to run in order so that the next one starts automatically after the previous one finishes?
3
votes
0answers
60 views

Why does the debugger not stop when a message is generated?

I am on version 10.1. I have enabled the debugger and I have checked the box in front of "Break at Messages" in the Debugger Tools Window. However most the time the debugger does not stop when a ...
19
votes
1answer
728 views

Difference between Fitting Algorithms

I am new to Mathematica, and I don´t quite understand, what the difference between the fitting algorithms Fit, FindFit, ...
8
votes
1answer
909 views

Animated Wave propagation using split operator method

Here is the state of the art: By solving the time-dependent Schrödinger equation, one obtains that the propagated wave function after time step $\Delta t$ can be calculated by applying the ...
2
votes
1answer
138 views

Package editor interface

Is there a way to get rid of the unused space on the left of the package editor? What is it's purpose if I configured Mathematica to not show In and ...
1
vote
1answer
243 views

Plot a numerical integration as a function of a variable

Suppose we have a function that is hard to evaluate analytically but a numerical estimate suffices. For example consider the $f(x,\Lambda) = \Lambda\cdot \sin(x)$ where $\Lambda$ is some parameter I ...
7
votes
7answers
454 views

Generate a list

Given the list o = {xmin, xmax, ymin, ymax}; how can I generate the following list? ...
2
votes
2answers
137 views

How to speed up a system simulation?

I need to simulate a series of nonlinear (and linear) with thousands of state variables. Here is a simple linear example ...
4
votes
3answers
198 views

Best way to represent a complex time schedule?

What would be the best way to represent a complex schedule in Mathematica ? For example a representation of the plain words schedule: "From Monday to Friday, from 8 am to 12pm and from 1pm to 4pm", ...
7
votes
0answers
269 views

How to generate a random flow graph?

A flow graph is a rooted directed graph that the root reaches all other vertices. I need to generate a random flow graph in Mathematica. My idea is to use ...
1
vote
2answers
55 views

Subsituting expressions for expressions

I'm trying to define functions using other functions, like so: f[a_, b_] := a/b; a[c_] := c; b[d_] := d; Now what I want to be able to do is two things: ...
0
votes
1answer
398 views

How can I use nonlinear model fit with multiple variables? [closed]

I have a data set with four entries. the first three entries correspond to variables in the fit x,y, & z. The fourth entry corresponds to the function value. I am trying to fit this data to a rate ...
3
votes
0answers
78 views

How to speed up solution of system of recurrence equations

I was wondering how I can improve the speed on this method for solving a particular system of coupled recurrence equations. The system is $$ \begin{align*} &V(m)=\alpha + \beta V(m+1)+\beta ...
2
votes
1answer
234 views

How do I download and export data from many weather stations?

I tried this code, which downloads data from several weather stations. ...
-1
votes
1answer
76 views

Factor out certain terms using Modulus but Mathematica requires that the modulus be an integer [closed]

Mathematica demands that the modulus be an integer. How do I work my way around this?
5
votes
1answer
522 views

How to plot the solution of a Partial Differential Equation?

My attempt. I need to solve numerically the Complex Ginzburg-Laudau Equation (CGLE): $$ \frac{\partial A}{\partial t}=\epsilon A-(1+i\beta)|A|^2A+(1+i\alpha)\nabla^2A $$ I'm using a uniform initial ...
0
votes
0answers
83 views

Difficulty solving an equation involving a couple of different powers

I have this semi-complicated equation to which I want to find an analytical solution for $\epsilon$. The equation is a s following: $$a^2 (2 b k \epsilon \sqrt{1 - \epsilon^2/b^2} - 2 c k ...
1
vote
1answer
204 views

How to properly use conditionals inside NDSolve

Currently I am working with Mathematica to learn the program, and I'm confused what exactly is wrong with this code. ...
21
votes
5answers
767 views

Removing a histogram's vertical edges

Let's say I have a histogram: Histogram[RandomVariate[NormalDistribution[10, 2], 500]] How can I remove vertical lines inside the histogram and keep only the ...
0
votes
1answer
143 views

Equation solving problem [closed]

I have this code: ...
0
votes
0answers
54 views

How do I plot an expression in mathematica? [duplicate]

I have the following mathematica expression: ...
1
vote
1answer
93 views

Constants from differential equations

I have a problem, I've solved 2 diff equations and I have: ...
4
votes
2answers
139 views

Using LeviCivitaTensor

I have 2 questions about using LeviCivitaTensor, based on the following session: The signs for the cross product seems to come out "opposite" of what I expected. Why is that? Did I miss anything? ...
4
votes
0answers
277 views

Help with Fourier analysis and filtering of an image

I am starting with the following image: For the curious, it is an STM scanned image of graphite. I am hoping to find some kind of periodic structure in the image related to the honeycomb structure ...
7
votes
1answer
230 views

Find and return the key with lowest value in association list

I am still new in Mathematica, and I need some help here. Suppose that I have an association ...
-2
votes
1answer
272 views

How to generate normally distributed random number [closed]

I want to sample or return random number from a distribution which is normally distributed with mean of zero and standard deviation of 1. I am using RandomReal[NormalDistribution[0, 1]] I s this ...
2
votes
2answers
85 views

Arrangements (?) from permutations of rows in a triangle, is there a simpler way to program this?

I am generally confused about integer valued polynomials, and how to count them. Trying to learn the subject I started by listing permutations of the rows in a lower triangular table: $$\displaystyle ...
1
vote
1answer
79 views

Replace symbols in output without evaluation

I found the Wolfram example for ExpandNCM but I want a more human-readable output form. I want to evaluate ExpandNCM, for example with ...
-3
votes
1answer
181 views

Why does Mathematica “sleep” when I don't work at computer? [closed]

I started using Mathematica few days ago. I'm running this code: ...
0
votes
0answers
45 views

StringLength function [duplicate]

allWeatherStations = WeatherData[]; fullformStations = FullForm /@ allWeatherStations; Tally[StringLength /@ fullformStations[[All, 1, 2]]]. This code not working. ...
2
votes
3answers
717 views

DSolve with assumptions

I'm new to mathematica and was wondering if someone could help me. I have a differential equation which is: $\frac{dy}{dx} = 1/2 y(1 - y)(a - y + a y)$ It has initial condition $y(0) = y0$ and ...
0
votes
1answer
86 views

How can I combine two plots? [closed]

I am interested in plooting x only from 0 to 1, and afterwards x^2, only from 1 to ... whatever ...
1
vote
1answer
116 views

Dealing Repeated pattern in StringReplace

A problem about StringReplace When I'm running into this problem possible [bug] ...
23
votes
2answers
605 views

Better way to visualize cylinder puzzle solution

The above puzzle has been a recent source of amusement in my clique. I decided to provide a visualization to motivate solution (here): My code: ...
0
votes
2answers
100 views

Plotting vectors using derivatives

This question stems from a previous question I asked here: Multiple Integral of equation including dx prime? An equation describing a gravitational field of a cuboid is given as: $V(X,Y,Z) = -G\rho ...
4
votes
3answers
359 views

How could I transform the YYYYDDD date string/Integer to YYYYMMDD date string?

suppose I have lots of YYYYDDD date Integers which look like(for example): ...
0
votes
4answers
170 views

How to trim the zeros from the right of a list? [duplicate]

I need to remove the zeros from the right of an integer list up to the first non-zero element. Such as {0,1,0,0,2,0,0}->{0,1,0,0,2}. Padding zeros can be simply ...
4
votes
0answers
118 views

Why the flat f[x] is treated as ghostHead_[f[x]]?

While reading this answer I feel confused. If we do not care any specific detail of the original question, then ybeltukov's answer essentially makes use of the following fact ...
3
votes
2answers
194 views

Solve the “Cheryl's birthday” puzzle using mathematica

The "Cheryl's birthday" puzzle has been circulating around, the backstory is available via wikipedia. The puzzle itself is reproduced here: Albert and Bernard just became friends with Cheryl, and ...

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