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
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0answers
42 views

Generating partitions of a set with a specified size of the parts [duplicate]

I tried the following (inspired by the answer here) myList = {a, b, c}; Needs["Combinatorica`"]; SetPartitions[myList] and I got this answer, ...
7
votes
3answers
343 views

Unexpected behavior of Unevaluated

Maybe it is about time I read some proper text about the main loop. Maybe I should not care (so much) about Unevaluated (as Leonid suggests). But I think this is an interesting question anyway. This ...
3
votes
0answers
172 views

I am missing a function like HoldPattern

Temporary message: I am planning to edit this question, making the examples less confusing and by moving the things that are confusing to a separate question For any confusion about expressions that ...
2
votes
1answer
296 views

Is it possible to treat starting values as variables?

I have a problem where I am using FindRoot a gazillion times over a grid of parameters. I need to allow the starting values to vary a bit with the parameters to get it to converge. Here is a simple ...
14
votes
3answers
201 views

What does `: Hold[$IterationLimit]` mean?

In this answer, what does the : Hold[$IterationLimit] part of the following construct do? ...
4
votes
2answers
215 views

why set values in this way doesn't work?

question is as follows define a list ttt={1,2}; and if I set values in this way {ttt[[1]],ttt[[2]]}={3,4} then the value ...
0
votes
2answers
77 views

How can i execute several Commands in one text file and use it in notebook?

I want to execute several commands in one text file and use it in notebook by Get[] command. for example: ...
15
votes
3answers
582 views

Comparing Mathematica expressions like diff

I am looking for a way to compare (or "diff") two Mathematica expressions, similarly to how to diff utility can compare two text files and report the differences. Has anyone already written such a ...
1
vote
1answer
976 views

How to run Mathematica using Mac Terminal

My question is so trivial and I'm sure most people in here know exactly how to do this, however I still don't know how to run Mathematica in Mac terminal! I need to use all the cores of my computer ...
11
votes
1answer
401 views

Triggering actions when a variable is set

Some built-in variables trigger actions when their values are changed: ...
1
vote
1answer
163 views

How can I import sound from within a Manipulate expression?

I want to import sound from a file, record, and import sound. ...
0
votes
0answers
22 views

Conflict among Permutations and Graph utilities once Combinatorica is loaded [duplicate]

I have tried to figure out and solve the problem of compatibility of Permutations and Graph utilities of Mathematica once the Combinatorica Package is loaded, but I failed :(. Could anyone explain me ...
0
votes
2answers
366 views

characteristic polynomial based on differential equation

I have this differential equation: $$\ddot{x}-\frac{1}{6} \dot{x} - \frac{1}{6}x = e^t$$ When I DSolve it looks like this: ...
1
vote
3answers
292 views

Minimize user defined function

I have a user defined function h[i_,j_] and I would like to find its minimum value over all integers $1 \leq i \leq 100$ and $1 \leq j \leq 100$ and $j \leq i$. I would just like Mathematica to try ...
20
votes
3answers
2k views

Fastest way to measure Hamming distance of integers

I am looking for a fast and robust way to calculate the Hamming distance of integers. The Hamming distance of two integers is the number of matching bits in their binary representations. I expect that ...
3
votes
2answers
664 views
15
votes
3answers
685 views

Custom functions by delegating options in a specific way and using core functions

I'd like to create a custom function that does essentially the same as a core function of mathematica but uses different default settings. Example: I want a Plot function that uses Mathematica's core ...
13
votes
4answers
395 views

Unencoding encoded URLs in a function

Is there a built-in function for decoding encoded URLs in Mathematica? I would like to convert an encoded URL, for example ...
20
votes
4answers
917 views

Accessing list elements by name

First, a bit of a long introduction to my problem: I only have a few weeks of Mathematica experience. I am creating a mathematica application that calculates some material properties of steel based ...
2
votes
1answer
285 views

Combining two notebooks

I have a notebook which contain all the variables and defined functions. I want to do two tasks. As an example, I want to find the density and energy which have equations in terms of above mentioned ...
4
votes
0answers
110 views

Is there a way to check whether two notebooks share the same variables?

When I code in Mathematica, I often re-use code from old notebooks which fulfilled a specific purpose; for example, one testing for soft matches in strings, or one that identifies outliers on a graph ...
3
votes
0answers
79 views

How to insert expression matching the format?

I would like programmatically to insert/write an expression at the current insertion point, but matching the current format, such as font size and style, so that it looks like the user typed it. ...
41
votes
9answers
8k views

Generating a Sierpinski carpet

I am trying to draw a Sierpinski_carpet. I have code that works, but I think there is a more elegant way to do than my way. Maybe I couls use Tuples or ...
5
votes
1answer
742 views

NestList and Euler's method

I am new to mathematica and so just experimenting with various programming constructs. Recently have been looking at NestList and how I could use this to implement ...
30
votes
4answers
4k views

Fastest way to calculate matrix of pairwise distances

It is a very common problem that given a distance function $d(p_1,p_2)$ and a set of points pts, we need to construct a matrix ...
1
vote
1answer
280 views

Automating sequential import of data from web

I am trying to import data from multiple web pages hosted by a single online source. The data is posted by the source as one data set per web page for each week of the year. I would like to import the ...
29
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 ...
1
vote
0answers
308 views

Data structure for a list of actions [closed]

The idea: I need to generate a sequence of events then run a "propagator" over the list of events where the "propagator" will update the state of the following event. I can then write functions that ...
13
votes
3answers
1k views

What is Mathematica's equivalent to MATLAB's filter function?

The MATLAB code filter(0.5,[1, -0.5], [1:10]) is equivalent to Rest@FoldList[(#1 + #2)/2. &, 0, Range[10]] I don't ...
15
votes
2answers
690 views

Need help coding/creating a recursive list

I have two lists A and B, each with 99 real numbers. I want to form a list, C, whose ...
1
vote
2answers
718 views
1
vote
2answers
486 views

Select rows from table by keys

I am looking for a way to iteratively select all sublists with the same ID (my 1st column, residual columns are AbsoluteTime entries). First, I obtained the list of ...
6
votes
0answers
258 views

Convert logical relational expression to / from disjunctive and conjunctive forms?

I would like to convert logical relational expressions in disjunctive form, e.g., $$(x \lt -1) \lor (-1 \lt x \lt +1) \lor (x \gt +1)$$ into conjunctive form, e.g., $$(x \ne -1) \land (x \ne +1)$$ ...
22
votes
3answers
411 views

Efficiently appending points to a NearestFunction

I have a program which works with a list of points (in 3D, but it could be in 1D as well, it won't make a difference). Within a loop, it keeps adding new points to the list. To calculate the ...
6
votes
2answers
6k views

Solving a tridiagonal system of linear equations using the Thomas algorithm

I'm trying to write a function that can solve a tridiagonal system of linear equations using the Thomas algorithm. It basically solves the following equation. (Details can be found at the Wiki page ...
2
votes
0answers
81 views

SetDelayed and avoiding function calls through memoization [duplicate]

I am fairly new to Mathematica. I am working my way through a number of books. I have been looking at the use of SetDelayed and want to confirm that my ...
0
votes
1answer
125 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}] ...
6
votes
3answers
2k views

Keep function range as a variable

Plot[2*x^2 - x + 2, {x, -1, 1}] plots a function of x from -1 to 1. As far as I can see, I cannot "save" this range in a variable: ...
30
votes
5answers
1k views

Voronoi diagrams for generators other than points

Any suggestions how to determine Voronoi diagram for sites other than points, as e.g. in the picture below? Input is a raster image.
18
votes
1answer
688 views

List manipulation to build a functional expression

Since Mathematica deals with Head[a, b] as an expression in this way The first Part of Head[a, b] is ...
1
vote
1answer
112 views

Avoiding unnecessary computations within loops

Consider the following data: test = RandomReal[{1, 2}, {10, 5, 3, 3}]; How can I do the following without the For loops, e.g. ...
6
votes
2answers
608 views

CorrelationFunction for vectors

Mathematica 9 has a new CorrelationFunction. Sadly the joy does not last long, as I can't get it to work with vectors. I would like to make a velocity correlation ...
3
votes
1answer
2k views

Executing a .m file from the Linux command line

I have some code in a file named Demo-3.m, It can be evaluated in Mathematica 9. The final expression in the file is ...
4
votes
2answers
736 views

Finding all/most roots of a discontinuous function more consistently?

I have the equation: f[x_]:=α Tan[α*a] - Sqrt[c - α^2] and ideally I want to find all of its positive zeros, given a and c, with variable alpha. The problem is ...
4
votes
2answers
183 views

How to achieve Set+Part like behaviour in custom Set function?

So I've been toiling away on my DataFrame package. I've been trying to get Set to work with it, but it seems it either can't be done (ie via ...
16
votes
4answers
1k views

Find the minima and maxima of a list

I have a list, such as: ...
0
votes
1answer
235 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. ...
15
votes
1answer
400 views

Is the sharing of variables in Module/Block within Compile documented behavior?

Today I noticed something, I think for the first time. When used inside Compile variable values within Module (and ...
9
votes
4answers
535 views

How to set Block local variables by code?

I need to create a user-defined Block function where the Block variables' values are defined by code. For example, imagine I ...
0
votes
1answer
126 views

Where do those nulls come from? [closed]

I have seen discussions of unwanted nulls in the output in the context of building lists with conditions on the elements, but that is not involved here. I would like to know where the nulls come from ...