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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12
votes
4answers
1k views

Pure Functions with Lists as arguments

Assuming I have two function: example 1: add[{x_, y_, z_}] := x + y - z add[{1, 3, 5}] If use pure function,I know I can write it as : ...
1
vote
1answer
109 views

How can I find the row differences of a matrix?

How can I compute the row differences of an m x n matrix to obtain an m-1 x n matrix; that is, given how do I obtain
0
votes
1answer
283 views

How can I improve my code with efficient mathematica built-in functions?

I have written a module for my assignment like below. V[n + 1] = rk[x[n], y[n] ,z[n], V[n]]; vs = V[n].V[n+1]; V[n + 1] = I want to modify it with efficient ...
2
votes
2answers
760 views

defining recursively a function with multiple if conditions

I am trying to recursively define a function which satisfies the following system of equations and which depends on two parameters $n$ and $l$, $$ \begin{align} A(x, n, l) &= F[ A(x,n-1,l) ]\\ ...
2
votes
1answer
126 views

Import a file only if it contains a certain pattern

Let's say I have three files containing: File 1: x y z 1 4 6 File 2: x y z 2 5 9 File 3: x y z 5 4 8 My goal is to import the data from a file only if in ...
9
votes
1answer
925 views

Coding mistake? [closed]

I have just started using Mathematica with v9.0. I am trying to follow a computation from a book on Fourier series with the function $f(x)=x$ on the interval $-\pi < x < \pi$. Here is the code ...
8
votes
4answers
526 views

Efficient code for the Ten True Sentences puzzle

I am trying to solve Ten True Sentences Puzzle. Take a look at the following sentences: The number of times the digit 0 appears in this puzzle is _. The number of times the digit 1 ...
0
votes
3answers
522 views

How can I fill in a matrix at every iteration of a Do loop?

I have a matrix whose dimensions are 26x26x3. For my assignment I have written a program which is using a Do loop (maxx=maxy=10,maxz=2): ...
0
votes
2answers
148 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 ...
4
votes
2answers
283 views

How can I find the lines that go through?

I have a 80 x 80 x 50 dataset. From this dataset, I get some curves. These curves are randomly seeded, by which I mean that their starting points have been chosen randomly. Below, you can find an ...
5
votes
1answer
1k views

How can I view the code implementing a built-in Mathematica function? [duplicate]

Possible Duplicate: What is the most convenient way to read definitions of in-memory symbols when we don’t have the source files? I would like to look at the code that implements ...
2
votes
3answers
280 views

How do I construct a pure function to extract data fields from records that are strings?

How can I get from data segment format to the final segment format with a pure function? The data fields are fixed length. There are no separators between the fields. a) list ...
12
votes
4answers
508 views

Can you recommend an efficient method for finding the least integer satisfying my inequality?

I tried find the minimum make $\frac{1}{2}+\frac{1}{2+\sqrt{2}}+\frac{1}{3 +\sqrt{3}}+...+\frac{1}{n+\sqrt{n}}>15$ Following code is so slow when I use condition ...
1
vote
1answer
191 views

How do I insert a piece of code in Mathematica?

In Fortran, I can use include "file" to insert a piece of code. Is there a similar method in Mathematica?
5
votes
1answer
237 views

Should Row be used in place of StringForm?

I've been using Mathematica for a long time, so I have a habit of using some of the older functions even when newer, better ones have been added to replace them. ...
8
votes
3answers
274 views

Grid without lines, but with dots

I want to build a grid to look like the top-left table shown below, but without an outside frame. Here is what I've tried to do: ...
46
votes
2answers
2k views

Once more on object orientation in Mathematica: does it have to be so hard?

Recently I came across a set of problems which would be solved most easily within an object-oriented approach. I first attempted to solve them by other means, but found the complexity of the code ...
5
votes
4answers
1k views

How to find the sum all even numbers of this sequence?

I have a sequence $(u_{n})$ $$u_1= 1, \quad u_2 = 2, \quad u_3 = 3, \quad u_{n}= -u_{n-3} + 3u _{n-2} +2 u_{n-1}, \quad \forall n \geqslant 4.$$ I want to list the first $20$ terms of this sequence ...
14
votes
3answers
641 views

How can I improve my code for drawing a tree?

This code draws a tree, but it's not in the functional style. ...
5
votes
3answers
314 views

More structure in Source Code/Notebooks

Mathematica is great for small and quick projects and has a great syntax. However as soon as a project grows I run into trouble. How do you scale and maintain projects in Mathematica? What is beyond ...
11
votes
8answers
509 views

Any built-in function to generate successive sublists from a list?

Given lst = {a, b, c, d} I'd like to generate {{a}, {a, b}, {a, b, c}, {a, b, c, d}} but using built-in functions only, ...
4
votes
2answers
232 views

About extension fibonacci

I have been trying to solve this problem, it worked slow. I know there is a efficiently way. How do I get it? The following is my code: ...
3
votes
1answer
130 views

How to make a pattern to change x^(2/y) to (x^2)^(1/y) for any x and y?

This might have been asked before. Please let me know if it is. I was looking at an interesting Mathematica question in students forum and trying to solve it, and a chance to learn more about ...
0
votes
1answer
2k views

Loops and subroutines [duplicate]

Possible Duplicate: Alternatives to procedural loops and iterating over lists in Mathematica I am new to Mathematica and not familiar with functional programming. In particular, I have no ...
1
vote
1answer
110 views

Draw from HistogramDistribution with ParallelTable

I wanted to check something, but ran into troubles using HistogramDistribution in combination with ParallelTable. The code does the following: Compute a HistogramDistribution of some sample and use ...
1
vote
3answers
2k views

How to create functions of arbitrary number of variables? [duplicate]

In the following code what would be the simplest way to generalize it to say some $N_f$ number of $z$ instead of just $z_1$ and $z_2$? ...
22
votes
2answers
488 views

How to implement FittedModel like objects

In the course of making some RLink wrappers I want to have some richer containers like Mathematica does with its FittedModel ...
6
votes
5answers
472 views

How to compile the code for generate Pythagorean_triple?

I am finding Pythagorean_triple, it worked slowly. I tried to compile, but it gives some warnings. I also use "Case" or "Do" ,both of them failed.I'm sure my CCompiler has been set correctly. How can ...
7
votes
3answers
985 views

Filtering elements from a list

Suppose that I have a list {{{2, 1}, {4, 3}, {2, 4}}, {{2, 1}, {4, 3}, {3, 1}}, {{2, 1}, {2, 4}, {3, 1}}, {{4, 3}, {2, 4}, {1, 2}}} I want to make a new list ...
7
votes
3answers
533 views

NDSolve and {C, K, Slot} and other built-ins as a variable name

The following problem is an exploration of what causes the error "Input is not an ordinary differential equation" in Mathematica as it seems to have changed from version 8 to version 9. Specifically ...
15
votes
3answers
2k views

Is learning to use Mathematica useful for pure theoretical research in Mathematics and Computer Science?

I am looking for opinions from Mathematica users about Mathematica itself. After reading the faq, I thought that in some sense I "wish to solve a problem using Mathematica" ... although I understand ...
9
votes
2answers
3k views

How to define a differential operator?

I have a linear differential operator, for instance, $L\left (\partial _{t} \right )=\partial _{tt} - 3\partial _{t} + 2$. I use it in 2 different ways: apply the operator to a function: $L\left ...
22
votes
3answers
2k views

Mathematica as a normal programming language

I'm interested in Mathematica's core language for both practical development and as an object of computer science study. Actually, the former is more of a means to the latter. I would like to create ...
3
votes
1answer
243 views

Computing closest set of points to each point in large set — running out of memory (arrays unpacking)

I have a large set of points in 3D and I'm trying to identify all the points that lie within a certain distance of each point. Then using this data store the vector between the pairs of points. I ...
5
votes
1answer
440 views

Progress indicator with shared variables

I'm trying to create a custom progress indicator for a parallelized computation, using Dynamic and SetSharedVariables to display ...
4
votes
1answer
255 views

speed up iteration with conditionals plus optimize memory usage

Given list1 and list2 whose elements are vectors of a certain (fixed) dimension, I am interested in the behaviour of a scalar ...
23
votes
3answers
2k views

Reading periodic elements from a large file

I have a large binary data file (big endian) with 100+ million "rows" of 11 elements, combination of floats and integers. This is the format: ...
4
votes
4answers
192 views

clean functional way to get first n rows that yield maximum rank

I have a matrix A and want the matrix consisting of the first n rows of A, having the same rank as A, where n is minimal. More generally, I want the shortest "start piece" of a list, such that some ...
4
votes
3answers
292 views

Creating Multi-Tabbed Grid with Preserved Contents and Overview Grid

I am in the process of creating an application/panel that will aide me in scheduling hours for my staff of ten or more. I am hoping to create a multi-tabbed grid within which I may collect data about ...
1
vote
1answer
258 views

Problem with function as an argument

I want to write a function like the following: s[u_, v_, x_, val_] := u[val]/NIntegrate[u'[x] v[x] + u'[x] v'[x], {x, 0, 1}] So I can evaluate something like ...
4
votes
2answers
549 views

Optimize inner loops

I'm Mathematica newbie so please be gentle :) I have this, heavily non-optimized part of code, which I would like to speed up. I have put all matrices to be RandomReal, but in my code they take ...
0
votes
1answer
403 views

How can I make many runs of a simulation and plot all the results with one expression evaluation?

I have many cells, starting with this first cell: ...
1
vote
0answers
276 views

Return Functions from parallel execution of module

I wrote a module which numerically solves an ODE using NDSolve. The result from this is e.g. either ...
6
votes
1answer
378 views

Why is MapIndexed better than mapping over a range?

Background I'm working on an application in which I need to create and control two sets of locators. I know from reading the Mathematica documentation and certain posts on Mathematica.SE that this ...
2
votes
1answer
447 views

Cournot Equilibrium

I'm trying to determine reaction functions of a Cournot equilibrium for $n$ firms using the same optimal condition, using the fixed point method. This is the method I'm using: ...
9
votes
5answers
476 views

Incrementing a number where each digit has a different base

Let's say I have a list, for instance {10,5,3}, indicating the bases for each digit of my 3-digit number. Using this basis, if I wanted to increment {8,4,1} a couple of times, here's what I would get: ...
2
votes
0answers
155 views
4
votes
3answers
577 views

How to make brute force coding more efficient?

Hi guys and guysettes, The little Mathematica I've been using/seen so far, it seems to be all about neat "one-liners" using the underlying functions and working with lists & maps to solve issues, ...
5
votes
1answer
234 views

How to create a Hyperlink within the current Notebook?

Using “Create Hyperlink” dialog window I can create a link to a tagged cell in my notebook (it's “Destination notebook: Current notebook” radio button). Now, I can't figure it out how to create such ...
7
votes
3answers
506 views

Rewriting For loop to FoldList or similar

In CrossValidated, the answer to a question on prediction of number of viewers of Gangnam Style is given in R. I have mapped the answer directly to Mathematica: ...