Questions on writing non-trivial programs in Mathematica. Do not use this tag for questions on plotting/graphics or for questions on doing mathematics with Mathematica, where the focus is more on the math than the program.

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1answer
86 views

How to plot multiple orbits with more than two functions

Using a program given to me (which was designed to have a particle orbiting another of infinite mass), I tried to extend it to the motion of two particles orbiting a common centre of mass. I have a ...
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2answers
125 views

Are there ways to create local variables analogous to a local variable in C++ and other languages? [closed]

There has been a great deal of discussion on local variables in Modules and Manipulate. If I am reading this correctly, local variables in a language such as C++ or C# are not exactly analogous to ...
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2answers
102 views

How to localize the symbols x,y, A, B in the following program? [closed]

I see a example in Paul Wellin's Programming with Mathematica An Introduction, 4th edition: ...
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1answer
450 views

Obtaining the envelope of an oscillating function and perform fitting

There is an elegant way to obtain the envelope of an oscillation function explained here http://mathematica.stackexchange.com/a/27854/15966 My question is how to modify the code below so I can fit ...
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1answer
101 views

ParallelTable not firing

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1answer
292 views

Implementing Rayleigh criterion method for finding the resolution of an optical system

I want to use the Rayleigh criterion to find the resolution of an optical system. I have two functions f1 = Sinc[x]^2 and ...
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1answer
1k views

Getting imaginary data from known real data using Kramers-Kronig relations [duplicate]

Possible Duplicate: Kramers-Kronig in Mathematica I am trying to get epsilon2 (imaginary part) from known epsilon1 ...
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1answer
135 views

Finding CPU time of more than one expressions

I want to find the computational time (CPU time) of my code. When I use TimeUsed or Timing commands they give the CPU time of ...
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1answer
46 views

Elegant ways of solving this file batching task

There are a batch of data files in a folder (dir = "D:\\Documents\\datadir"), each of which consists of a list of data items, one per line. Each data item is a pair ...
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1answer
175 views

Is it possible to build/simulate/extract data from a System Modeler model completely inside a notebook using the MathModelica language syntax?

See examples in: http://www.mathematica-journal.com/issue/v10i1/contents/MathModelicaPaper/MathModelicaPaper_2.html It seems to be ruled out by the statement (Chapter 2 intro): "The subset of the ...
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2answers
142 views

Improving code for comparing and modifying nested matrices

I have a matrix such as: ...
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1answer
206 views

Using Findroot within a loop

I am trying to get solution to an equation in a loop. The isolate equation works ...
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1answer
120 views

A problem with set values

The following code is just an example to clearly explain my problem. Assume that : ...
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1answer
60 views

How to put some values from a list into a function in a Do loop

I want to program a code in MATHEMATICA in order to calculate some values in different iteration. For example, assume this list: list={1,2,3,4,5} Now assume that ...
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2answers
110 views

Finding lags of time series with `Do`

I have generated two time series, S[t] and P[t] as follows: ...
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1answer
76 views

How to write series of Do[ ]'s with a single Table[ ]?

Edited to provide more information (sorry I don't know how to format matrices here) I would like to replace: m = 4; ...
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1answer
123 views

Holding Input Windows

I am creating a Mathematica document which contains a list of proofs in various fields of Mathematics so that I can easily review whenever I would like. First, I create a large set I call 'proofs' ...
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votes
1answer
222 views

How to combine two usages of # into one and speed up the code?

I have a function num with two variables, matf and matg. How can I combine the last two lines of code below into one? The code is aimed to find out the maxiaml count bel when we give each $i3 = ...
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1answer
184 views

Pattern match with Table for matrix dimension check

In Mathematica, often an expression involving matrices will encounter dimension mismatch errors, like we are multiplying a 3x2 matrix to a 3x4 matrix. Below we define a new symbol Dim, which can be ...
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1answer
226 views

Why does memory run out when adding same-sized matrices in a loop?

I have written a module that it generates a 101x101x51 zero matrix at first. At every iteration, it generates a list by funct1 and based on this list, if list is empty it gives the previous result. ...
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1answer
40 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. ...
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1answer
68 views

Eigen energies of 2D time independent Schrödinger equation

Firstly, I am aware that a similar question of this type was asked, but it was not helpful as it was only one dimensional (so please don't mark my question as a duplicate) The trouble I am having is ...
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votes
1answer
25 views

How to combine two or more groups while selecting form the unbalanced panel data if the number of obs is less than a scalar in certain groups

I have an unbalanced panel data. I want to calculate group statistics for each group. However, if ith group has less than K obs, then I want to combine ith and (i+1)th groups to calculate group ...
0
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1answer
81 views

How to improve this function that selects parameters from arbitrary distribution using Recursion?

Below, I have defined a function using Which to select model parameters based upon various conditions. My questions are: Is there any danger in writing this function using Recursion? Is there a more ...
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votes
1answer
41 views

Why does this cause an error? [closed]

In[73]:= f[x_] := Save["C:\\Users\\user\\Desktop\\file", x <> x] f["###"] During evaluation of In[73]:= Save::sym: Argument ...
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1answer
85 views

converting DO loop into NestList form

I would like to rewrite this Do loop using NestList. Can you help me? ** DO loop ...
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1answer
33 views

New output cell generated for each run of a GraphicsGrid - is there a way to simply update the same output cell each run?

I have a Code cell that generates a set of plots in a GraphicsGrid[]. Each time I execute the Code cell, a new Output cell is generated. Is there a way to simply update a single output cell instead ...
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1answer
67 views

Data file organized in strings

I am working in a data set : The original question, They are strings of thousands stars,and each one contains a lot of parameters, and the following item is called identifies, they are the names ...
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2answers
156 views

Exctrating data information from a file.txt

I really did previous long search in the site and I couldn't find any answer that might help me. So I am asking it. I have the following data set, ...
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1answer
61 views

How can I assign a vector unknown function to solve the ODE system?

I noted that using non-scalar variables is convenient when a system of differential equations is governed by a process that may be difficult to express symbolically. Taking a example from the tutorial ...
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1answer
49 views

Programming a series involving alternative log expressions

This is likely my error but I cannot see it. I define a vector: x1 = {{{2, 2}}, {{2, 1}, {3, 1}}, {{3, 2}}, {{2, 1}, {5, 1}}} If x1[[ i, 1,2]] is 2, I would like to find $(\log$ x1[[ i,1,1]]$^2$). ...
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votes
1answer
133 views

Turning a 2D 3 body problem into 3D not so easy?

I have programmed a 3 body problem, that can in theory work for more than 3 bodies. I apologize in advance for the length of the code that I posted, I don't really know how much one would need to ...
0
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1answer
117 views

Need help in understanding code [closed]

I am just beginning with Mathematica. I have received this code to study. I am not able to follow this particular section. I have tried looking it up on many forums, with no answer. Can you help? ...
0
votes
1answer
50 views

Help with programming(using list) [closed]

I would like to make a program which gives me what is the greater natural number "n" less than an arbitrary given natural number "k" which satisfy: for each prime divisor "p" of n, p^2-1 divides n. I ...
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votes
1answer
146 views

For-loop only executes first line in body [closed]

I have a simple For[] loop: ...
0
votes
1answer
134 views

Using a LocatorPane

I have a network of a power grid where the edge are the power lines and the vertices are loads or generators. I was wondering how I can import an image into Mathematica to derive some sort of ...
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votes
1answer
87 views

How to produce functions [closed]

I want to produce n functions. For example, assume that by giving n=3, 3 definite integrals will be created, like the following: ...
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1answer
282 views

Mathematica Implementation of Householder’s Method

I typed the Householder code in this paper, which starts on page 7. The code is: ...
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1answer
181 views

Defining a new matrix product of matrix function [closed]

Suppose I have two matrices A, B, whose entries are functions of x. Suppose they are 2*2. In the product, each entry is of the form $\sum_k A_ik B_kj$. There are two summands corresponding to k=1,k=2. ...
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1answer
386 views

Heat Transfer equation by numerical methods

I want to solve the following heat conduction equation using numerical methods: D[u[x, t], t] -alpha*D[u[x, t], {x, 2}] == 0 u[x, 0] == 1/(1 + x^2)^0.25, u[-10, t] == u[10, t] == 0, ...
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1answer
834 views

Evaluate function of two variables using nested Do loops

Is there a more efficient way of evaluating a function of two variables on a rectangular grid the the following nested Do loops? ...
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1answer
258 views

A problem on generating convex hull

For example, I typed the following: ...
0
votes
1answer
103 views

Collecting roots of different equations and create a list

I solve two equations and have two solutions one by each equation. I want to create list of these roots. Could anyone please help me? Appreciate it. m02R150 = FindRoot[P1 == 0, {E1, 0.07, 0.1}] ...
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2answers
137 views

How to obtain a smaller-sized output from Solve

I am solving a system of 15 simultaneous linear equations using Solve. On running the code, I get a message saying "A very large output was generated" with options ...
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1answer
303 views

Problem with Eventlocator Method for NDSolve

I want to solve the ode and plot the solution v[x] for different values of parameter a where ...
0
votes
1answer
405 views

How to solve a problem in relative motion?

I have a project due tomorrow that I have been struggling with for a month. I am utterly stumped, any help would be appreciated. The problem is: There is a ferris wheel, 30m in radius, set 80m ...
0
votes
0answers
20 views

Debug package with command line arguments

I'm creating a package that takes as arguments input from the command line using $ScriptCommandLine. What's unclear to me is how to best debug this package. How do others perform these tasks? I ...
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votes
0answers
30 views

$MessageList inside and outside Block[]

Why does 1/0 $MessageList return ComplexInfinity whereas ...
0
votes
0answers
31 views

Retrieve rendered graphics via WSTP

I am planning on using Mathematica as calculation- and rendering backend for an application, i.e.: Call Mathematica via WSTP and by using EvaluatePacket have it ...
0
votes
0answers
42 views

Trying to write a program to find an approximate harmonic function on a given graph using relation method

So given an undirected graph with two vertices that have fixed values assigned to them, a harmonic function is a function that assigns values to all other vertices such that the value assigned to each ...