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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5
votes
2answers
384 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 ...
0
votes
0answers
49 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 ...
0
votes
1answer
87 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 ...
1
vote
1answer
103 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: ...
2
votes
2answers
133 views

How to plot points with error circles on map with latitude/longitude grid

I am currently working on a project to model the location of icebergs in the northwest atlantic. When an iceberg is sighted, an error circle is plotted around it (with a bivariate normal probability ...
4
votes
0answers
76 views

Using mathlink/WSTP with fortran

I would like to access Mathematica functions from within a Fortran program. I am unsure how to start (which is probably related to my lack of up-to-date Fortran knowledge). Is it necessary to write a ...
1
vote
1answer
81 views

Hypothesis Testing and Formatting Output

I am trying to write a function that tests hypotheses and gives me a nice table but I can't. I need forum's help. For example, I have the following data ...
5
votes
0answers
106 views

How to construct custom operators with precedence?

I need to combine data structures in operations analogous to addition, subtraction, multiplication and division (and more). I need more than one operation of each type, i.e. more than one method of ...
2
votes
1answer
182 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 ...
1
vote
1answer
63 views

Ways to protect certain parts of expressions

I am currently working on a quantum mechanics problem where I try to find equations that relate different states of a many-body system. The states are described by sets of pairs of integers, like ...
0
votes
0answers
25 views

Iterating a model with 2nd order difference equations using Manipulate [duplicate]

I have a model including first and second order difference equations. It works for the case of first difference equation, which is below: ...
4
votes
2answers
136 views

Nested mapping of a function

If I use the construct f[#] & /@ f[#] & /@ f[#] & /@ {a, b, c} my function works, but if I use ...
4
votes
2answers
123 views

Finding column-wise ranks of values in a multidimensional list

I often have to find ranks of values in a list. However, Mathematica does not have built-in functions for that, or may be I'm just not aware of them. I can easily find ranks of a row/column vector. ...
0
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 ...
5
votes
3answers
367 views

Easiest way to create a binary variable

Binary variable is often used in applied statistics. However, I had a hard time to figure out how to create it. Somebody might have better idea how to do it. I have two variables say x and y as ...
1
vote
0answers
104 views

Simulations using alternative initial conditions

With help from some of you guys here in this forum, I have developed the following code, which works perfectly. My questions are: how to automate the simulations with varying initial conditions. In ...
1
vote
1answer
118 views

Using FindMinimum with matrix input

I define the following function which spits out a number S when I feed it a dxd square matrix: ...
0
votes
0answers
70 views

Stringing functions together

My professor introduced Mathematica to my class for the first time this week and gave us the following assignment. Also a disclosure that this is the first computer science class I have taken and the ...
2
votes
0answers
95 views

How to efficiently find parts of a string with beginning and ending specified?

I'm trying to find specific URL addresses from a html document. The addresses can be found between the strings "href=\"" and "\" class=\"listing". The problem is not including strings like this: ...
0
votes
1answer
90 views

converting DO loop into NestList form

I would like to rewrite this Do loop using NestList. Can you help me? ** DO loop ...
0
votes
0answers
59 views

Modifying Game of Life code so that the lattice can be seeded with life forms

I want to modify Game of Life code so that the lattice can be seeded with one or two new life forms like: ...
10
votes
1answer
173 views

Copy Built-in function to new name

It is know that some built-in functions are system function and changing their properties may cause trouble. Suppose for example I want to change features of Cases: ...
2
votes
0answers
92 views

How can I do multiple (double) integral with periodic boundary conditions?

I am trying to do a simple double integral $\int_0^l \left[\int_0^l h^3 h_{xxx}dx\right]dx$ with periodic boundary conditions $h[0,\tau]=h[l,\tau]$ $h_x[0,\tau]=h_x[l,\tau]$ ...
0
votes
1answer
136 views

NDSolve with initial condition: initial conditions did not evaluate to an array of numbers of depth 1(for 1D) or 2 (for 2D) on spatial grid

I have the following naive code to solve a PDE in two spatial dimensions (x,y) with periodic boundary conditions: ...
7
votes
3answers
511 views

Mathematica style guide?

I encountered this site today https://code.google.com/p/google-styleguide/ regarding the programming style in some languages. What would be best programming practices in Mathematica, for small and ...
4
votes
1answer
121 views

ControlType -> None Vs. Module inside Manipulate (i.e. making everything local)

I'm building a program on another one made available in the Wolfram Demonstration Project. I've noticed that in the original code (working flawlessly) many variables were made local inside the ...
11
votes
6answers
397 views

For a given expression: if it appears, remove it, but if it is absent, add it

While reformatting Szabolcs's code from (42660) I noticed this interesting operation: ...
2
votes
1answer
72 views

Are there methods to serialize and deserialize large calculation runs? [closed]

I have a fairly large calculation to map an electric field over large areas (square kilometers). This runs for a fairly long time. Are there ways to serialize the current state of a running ...
0
votes
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 ...
1
vote
0answers
93 views

Code turns dark blue after trying to run it [closed]

I have a large amount of data in my N-Body Code. I imagine Mathematica doesn't really like this, but is there any other reason for my code turning a navy blue colour after I try to run it?
0
votes
0answers
61 views

Define column types in a Dataset - Failure on append and Typesystem

I have a basic function that populates a Dataset according to user specified parameters. ...
1
vote
1answer
127 views

How would I obtain a list of column names in a Dataset?

I really love the addition of Dataset to Mathematica. I would like to write a basic utility function that exports a Dataset to Excel. Is there a way to get a list of column names from a Dataset?
-3
votes
1answer
93 views

How to make X and Y = Z? [closed]

Hello I have a big question, maybe it's extremely easy but for now I'm unable to make it work. I'm a programmer and what I need to do is for example: if X = 2 and Y = 1 then Z = 1 if X = 3 and Y = 1 ...
4
votes
2answers
192 views

How would I programmatically add a row to a Dataset?

I would like to use a Dataset to track the process of a lengthy calculation over a large volume of material. Dataset appeals to me because of the power of the queries and it also looks like it may ...
0
votes
0answers
12 views

all does not work [duplicate]

Thanks blochwave for giving me a detailed answer, but I have already used all these methods and none of them has worked well, it is clearly written in mathematica "get help" file that the Timing[] and ...
2
votes
1answer
143 views

How to speed up my code about Divisors?

This code is about PE496 In[21]:= ParallelSum[n*Count[Divisors[n^2], a_ /; n < a < 2 n], {n, 1, 10^5}] // AbsoluteTiming Out[21]= {5.987342,10724527832} I ...
0
votes
1answer
160 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 ...
0
votes
0answers
39 views

How to simultaneously change variables shared by several functions?

I designed a fit program, the framework follows: a matrix build function: Q[a_,b_,c_,d_]; several matrix manipulate functions shared the variables {a,b,c,d} like this: ...
0
votes
1answer
91 views

InterpolatingFunction used to work with mathematic 7 but not working with mathematica 10

This code is used to work perfectly with Mathematica 7 and now it is not working with Mathematica 10. Any help is appreciated. CL05 = InterpolatingFunction[{{0.5, 11.99999999999999}}, {1, ...
9
votes
4answers
333 views

Interactively inspecting parts of an object

There have been times when I want to find the structure of an object in order to extract some part of it. For example, extracting the x and y coordinates from a Graphics object generated by Plot. I ...
0
votes
1answer
76 views

How can I use manipulate on multiple lists within a function?

So I have my N-Body Problem set up like so, and I can plot it in ListPointPlot3D, but I cannot figure out how to stick this into a manipulate function. ...
7
votes
2answers
372 views

How to get short definition of all built in Mathematica Functions?

The first post in "Mathematica Weekly Newsletter - Tuesday, December 30, 2014" really attracted my attention as I was always looking for a complete list of built in Mathematica functions with short ...
4
votes
1answer
224 views

A problem about Steffensen method

Two days ago,I asked a question about bisection algorithm. Thanks for Michael E2 giving me a good solution My algorithm 1, I use the bisection algorithm to generate a initial value that contain a ...
7
votes
3answers
454 views

Implement the Bisection algorithm elegantly and easily

Description: Rencently, I have finished my course Numerical Analysis, so I'd like to implement many algorithm that I have learned from that course.By this practice, I hope that I can improve my ...
0
votes
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 ...
1
vote
2answers
75 views

Subroutine execution repetition

I like to write second and third lines repeated operation only once as a separate module with some Name. In each main program line a set of different set boundary conditions data is given,Name invoked ...
1
vote
2answers
115 views

Expressions containing globally undefined symbols inside a function where they are defined

Consider the following code. f[a_,b_]:=x; Clear[a,b]; x=a+b; f[1,2] It returns a+b. However, from a certain viewpoint, one ...
0
votes
2answers
162 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, ...
13
votes
11answers
1k views

Divide all but the maximal element in a list by 10?

I have a list of numerical data, and I want to write a program that will keep the maximum as it is, but reduce the rest by certain factor (such as 10). For example: ...
4
votes
0answers
157 views

Can I define an axiomatic (Boolean algebra) system and prove theorems using Mathematica?

The general question is Can I define an axiomatic system and prove theorems using Mathematica? The more concrete one is about Boolean algebra. I consider this axiomatic Boolean algebra system ...