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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0
votes
2answers
76 views

FindShortestTour to solve Traveling Salesman Problem

I'm trying to write my own code to find the shortest route but I'm lost on how or where to start. Does anyone have any idea how the FindShortestTour function works? What type of algorithm or structure ...
8
votes
3answers
544 views

How to ensure that Polygon[list] plots a simple polygon?

Consider the following code which plots a triangle. p = {{0, 0}, {.2, 0}, {0, .2}}; {Cyan, Polygon[Dynamic[p]]} // Graphics Then adding (for example) ...
58
votes
3answers
9k views

Is there an open source implementation of Mathematica-the-language?

I've seen questions before such as "What is the best open-source equivalent for Mathematica?", but that specific question (and that line of inquiry in general) cares more about the computer algebra ...
209
votes
21answers
26k views

What are the most common pitfalls awaiting new users?

As you may already know, Mathematica is a wonderful piece of software. However, it has a few characteristics that tend to confuse new (and sometimes not-so-new) users. That can be clearly seen from ...
6
votes
2answers
325 views
+100

Adapting “Find and Replace” functionality to work with Patterns

I was thinking if there is something like Find and Replace (Crtl+F) functionality adapted to work with patterns. Probably not, but it seems possible to create this with some effort and skills in ...
0
votes
1answer
57 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 ...
6
votes
2answers
279 views

Association and rudimentary object-oriented programming

Doesn't Association provide us rudimentary object oriented programming via constructs like ...
7
votes
3answers
196 views

How to speed up auxilary DoolittleDecomposite function?

The Doolittle Decomposition algorithm as below: $$A=LU$$ where $A= \begin{bmatrix} a_{11} & a_{12} & \cdots a_{1n}\\ a_{21} & a_{22} & \cdots a_{2n}\\ \vdots & \vdots & \vdots ...
341
votes
13answers
69k views

Where can I find examples of good Mathematica programming practice?

I consider myself a pretty good Mathematica programmer, but I'm always looking out for ways to either improve my way of doing things in Mathematica, or to see if there's something nifty that I haven't ...
3
votes
2answers
1k views

How to linearize an expression automatically?

I would like to automatically linearize some long equations in the scope of variational calculus. Here follows an example of what I need to do : Given two variables $a_1 = q_1 + \delta q_1$ and $a_2 ...
2
votes
1answer
104 views

How can I invoke the solution of NDSolve to determine a parameter in my equation just inside NDSlove?

I am trying to solve a differential equation by NDSlove for $h(x,t)$. It reads $$h_t=h_{xx}-V_h-\lambda(t)$$ where $V_h$ is a given function of $h(x,t)$ denoted by ...
5
votes
1answer
115 views

How is LHS = RHS; … ; RHS (nontrivially) different from … ; RHS

I'm trying to understand how Mathematica thinks about the results of Set. Suppose we perform LHS = RHS. I'm focusing on when ...
0
votes
2answers
60 views

Diophantine and odd

need to resolve this Diophantine equation, but with the condition that a, b, c belong to the set of odd numbers from 1-51, as I write this condition in the code ...
27
votes
4answers
1k views

What tools can help in realizing tail recursion?

I had nice discussions with Leonid and Rojo that got me interested in tail recursion. Tail recursion is not always easy to realize with Mathematica, so it would be nice to have some tools to help with ...
7
votes
1answer
132 views

Relaxation of Mass-Spring System with Pinned Masses

Problem Assume that four masses are connected to each other by springs while two of them are pinned down at their initial positions. Find the position of masses when system is at its minimum ...
-1
votes
0answers
23 views

How could I speed up a code including a Module with many functions

I have implemented a big formula through the mathematica function Module. Within this module a lot of definitions are made (i.e. function[x_]:=). The code are working well but it is too slow. I am ...
6
votes
4answers
203 views

What is shorthand way of Reap list that may be empty because of zero Sow

Sometimes because of conditionals, you cannot guarantee that Sow will be called at least once. Reap[Sow[1]][[2,1]] results in ...
2
votes
1answer
101 views

How to define the Bernstein function like the built-in BernsteinBasis?

We know the Bernstein function defined as below: $$B_{n,i}(u)=\binom n i u^i(1-u)^{n-i}$$ And we define $B_{n,i}(u)=0$ when $i<0 $ or $i>n$ In addition, the first derivative of $B_{n,i}(u)$ ...
26
votes
4answers
986 views

Can a function be made to accept a variable amount of inputs?

I have a function that takes two inputs and processes them for a single output. What I need is one that can take a varying number of inputs. and process them to a single output. Is this possible in ...
0
votes
1answer
54 views

cross point of intersecting lines [closed]

What is the easiest way to find the crossing point of two intersecting lines passing lets say through points line1 = {p1,p2}, line2 = {p3,p4}?
1
vote
1answer
93 views

Separate output screen; clearing (cleaning) output screen

Is there a way to split the screen so that the code is on top visible, and execution of code look at the bottom? Is there any way to clean the screen from previous runs, so that the result of ...
47
votes
0answers
1k views

Is this 30% slowdown in Mathematica 10 due to DownValues lookup time?

Running several numerical self-programmed packages I realized already some time ago that Mathematica 10 needed between 20 and 40% more time. I did already report this of course with a simple example ...
0
votes
0answers
29 views

$MessageList inside and outside Block[]

Why does 1/0 $MessageList return ComplexInfinity whereas ...
12
votes
2answers
1k views

How do I automatically evaluate a cell when a notebook is opened?

I'm trying to put together a GUI in Mathematica and need to evaluate one cell to kick that off. Is there a way to automatically evaluate that cell when the notebook is opened? Here is an example of ...
0
votes
1answer
24 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 ...
2
votes
1answer
69 views

How to package a function for export?

I often post code for functions on Stack-Exchange, and then later find that they are unexecutable - that people can't use them because I mistakenly omitted some private functions or values that are ...
1
vote
0answers
36 views

How to use RunProcess to run python interpreter

In a related question How to use RunProcess to import external function? @taliesin provides a very nice answer illustrating using RunProcess to launch a GO http server. Has anyone, or does anyone ...
4
votes
0answers
99 views

Delete duplicates by a criteria

Given that I have a set of points as below ...
0
votes
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 ...
2
votes
2answers
141 views

Issue with Set function

Tables often come with column headers. Indexing the columns with the header is a natural thing to do. Although a proper dictionary is the usual solution in such a case, I find it often practical and ...
4
votes
1answer
58 views

subtleties about variable shadowing in Block[]

Let' s consider this packege : BeginPackage["myProgram`"]; myProgramF::usage = "arg + 1"; Begin["`Private`"]; myProgramF[arg_: 0] := arg + 1; End[]; EndPackage[]; ...
0
votes
2answers
129 views

Spiral roots, how?

I found this picture on the net, as I can play in mathematica
1
vote
1answer
35 views

Implicit region is not “valid” in ParamatricNDSolveValue function?

I am trying to solve a geometric problem with relation to my Schrodinger equation and its boundaries. Here is my code: ...
1
vote
1answer
96 views

Perceptron: Do loop not returning a value

I am trying to write a function that finds a simple best fit line for some data (Perceptron algorithm). Sadly it returns no output at all. Here's the code below: ...
-1
votes
0answers
24 views

Feasability question about object tracking in 3d space

Is it possible to use 3 different webcams to track an object in an xyz axis. If so, how would one do it?
3
votes
2answers
138 views

How can I create a 3D representation of an object with known coordinates and adjacency table in mathematica?

Basically I want to create an object with specified coordinates and adjacency table, like in page two of this article. I'm completely new to using Mathematica, any help would be great! EDIT: So I ...
3
votes
1answer
135 views

Why even try the semantic constraints, if expression can't match the pattern structure?

This result is unexpected: Trace[MatchQ[{7}, {_?NumberQ, __}], NumberQ] (* -> {{NumberQ[7], True}} *) Why evaluate ...
13
votes
2answers
471 views

Generating Gelfand-Tsetlin patterns

I am doing some research on some combinatorial object called GT-patterns. They are generated from three parts of data. Two integer, partitions (sequences of weakly decreasing numbers), $\lambda = ...
5
votes
2answers
332 views

Find permutations with constraints without using Permutations

EDIT: To clarify, the bottleneck right now is available RAM, so any answer should keep that in mind (I cannot store all T! lists of length ...
3
votes
1answer
200 views

How to download pictures from webpage automatically?

Today, I read a good web page about love which owns many beautiful pictures. It is fussy for me to download every picture hand-by-hand, so I'd like to use Mathematica to do this case automatically. I ...
9
votes
3answers
160 views

Implement settable properties

I am looking for advice on implementing the following. (It is possible that the answer is that it is simply not a good idea to do this.) I would like to have an object similar to ...
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 ...
1
vote
1answer
125 views

Read expression from Mathematica via Mathlink C++

This is a simple C++ program to send an expression to the_Mathematica_ Kernel and get its response. ...
2
votes
3answers
135 views

How to extract both first and last rows of each group from unbalanced panel data

This is a follow up question form my last question click here. I have unbalanced panel data such as : ...
2
votes
3answers
179 views

How can I use NestWhileList instead of While in this case?

OK, the problem occurred when I challenged with Project Euler No. 10 The sum of the primes below 10 is 2 + 3 + 5 + 7 = 17. Find the sum of all the primes below two million. My code is: ...
6
votes
1answer
193 views

How can a function know in which function it was evaluated?

Hello my second question here might be very hard. I am asking for something "magical", if i define a function g and i call it inside a function f, how can g have information about the outer function ...
3
votes
1answer
104 views

How can I overload a function with multiple bracket-slots so f[a][b] and f[a] can coexist?

Maybe this is not even possible: I want to create a function f that can have two input brackets like: f[a_][b_:1]:= a*b and ...
2
votes
2answers
61 views

Need help updating an old Mathematica worksheet

I found a notebook that symbolically applies the multiple time scales method to any differential equations. I don't like just using other people's code so I am going through the author's work line by ...
17
votes
2answers
2k views

Open Excel file with Mathematica

I would like to open an Excel file and manipulate it as a COM object. While I'm able to open an instance of excel with ...