# Tagged Questions

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.

423 views

### How can I hold UpValues but evaluate other expressions?

Consider these definitions: own = "OwnValue"; down[_] = "DownValue"; sub[_][_] = "SubValue"; N[n] = 3.14; _[___, up, ___] ^= "UpValue"; The attribute ...
815 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 ...
5k views

### Mathematica Bifurcation

Continuing with the same question I have posted earlier I would like to find the equation of the stable fixed point curve using my graph, i.e. from the curve somehow find the equation for $x=f(x)$. I ...
293 views

### Return a Part by Reference? (For accessing hierarchical / structured data)

Is there a way to return a part of a list by reference, for reading and writing? I want to do this so I can easily manipulate "rule-styled structured", i.e., hierarchical data that is loaded from a ...
510 views

### Collatz optimization

I'm VERY new to Mathematica programming (and by new I mean two days), and was solving Project Euler question 12, which states: Which starting number, under one million, produces the longest [...
1k views

### Problem with Fourier coefficients

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 ...
503 views

### Generating a matrix using sublists A and B n times

I want to write a function that generates a square matrix from sublists. My sublists are a = Range[0, x, 0.5]; b = Range[0.25, x + 0.25, 0.5]; Suppose x=2, then I ...
307 views

### Cases[data,Colon[key,_]] vs. Cases[data,key:_] toward XPath, XQuery

Exploring methods to index and search tree-structured key:value pairs via named-entity index (key paths) as opposed to Position-based indexing. Using Rule as <...
395 views

### Replace with position and order number

question conversion1 : Convert "[AA]AB[AA]BB[AA]B[AA]CCC" to "[A1A2]A3B1[A4A5]B2B3[A6A7]B4[A8A9]CCC" conversion2 : Convert <...
335 views

### How can I use Max[] in a function that is passed a list not find the max of the list

For most functions in Mathematica, passing them a list will call the function on each element of the list. For example: ...
622 views

### Using the result of Solve in subsequent calculations

I'd like to know how to use the results of Solve in later calculations. Here's what I'm doing now: This is my expression ...
6k views

### Having used Mathematica as a “gateway” language, where to from here?

I have been using Mathematica for about a year. It is the first language that I have attempted to learn. I'm still very much a newbie, but there are moments I feel more like I am waving than drowning. ...
2k views

### Reconstruct text pages cut by shredder

Q1: I have a page of a printed text file, but it was cut by a paper shredder (from top to bottom). You can download all the paper fragments here. Here are some of them. How can I reconstruct it? Q2:...
9k 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 ...
3k views

### Finding a percolation path

I would like to examine percolation on a random lattice. To be exact, I wish to find the minimum length of a 'bond' needed such that the leftmost site can be connected to the rightmost site. Here is ...
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.
520 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 ...
640 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 ...
667 views

### On drilling holes with minimal redundancy (and with colors!)

The old Mathematica package GraphicsShapes featured the function PerforatePolygons[], which drilled a hole in any ...
3k 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 ...
502 views

### Underlying Algorithms for List Manipulation Functions

Does anyone know, or know of a link for the underlying algorithms used for list manipulation functions? Specifically: Union with and without the ...
538 views

### Dealing with nested options

OptionValue allows for recent versions of Mathematica (I think as from 7) to easily access optional parameters if they are explicitely given to a function or their default values otherwise. For big ...
2k views

### How can I type-check the arguments of a Mathematica function?

(For educational purposes) I defined the following functions: Translation (in $\mathbb{R}^2$): trM[vec_] := {{1, 0, vec[[1]]}, {0, 1, vec[[2]]}, {0, 0, 1}} ...
434 views

### Triggering actions when a variable is set

Some built-in variables trigger actions when their values are changed: ...
240 views

### CSS Selectors for Symbolic XML

Symbolic XML is a convenient way of managing XML in Mathematica, at least for casual use or small tasks. Here and elsewhere you can find examples of XML handling in Mathematica, including XSLT/XPath ...
2k views

### Is it necessary to have a prior computational background or is it possible to learn Mathematica as a first programming language?

I have a background in economics and I'm very interested in learning Mathematica but I'm afraid of starting out because I have seen that most programmers already have a good background in some kind of ...
1k views

### Reading from STDIN, or: how to pipe data into Mathematica

Today I tried using Mathematica's plotting capabilities to display the output of a C++ program. This made me wonder whether it is possible to somehow tell a Mathematica script to read from STDIN and ...
2k views

### Generating an ordered list of pairs of elements from ordered lists

I have a pair of ordered lists. I want to generate a new ordered list (using the same ordering) of length n by applying a binary operator to pairs of elements, one from each list, along with the index ...
1k views

### Splitting up delimited data in lists

One task that I frequently find myself doing in Mathematica is splitting lists into lists of sublists, using specific elements to define the break-points. This is particularly useful with imported ...
366 views

### Using Apply inside Compile

In this great answer a compiled version of the Nelder-Mead algorithm is presented. Since it works on arbitrary dimensions (i.e. arbitrary number of arguments), it has to use apply on the objective ...
843 views

### Dynamic Programming with delayed evaluation

By using dynamical programming, we can save intermediate steps for recursive relations, as in f[n_]:= f[n] = f[n-1] + f[n-2] However, this only stores ...
398 views

### Restrict Sensitivity of Locators in LocatorPane

We can restrict the movement of locators in a LocatorPane as follows: In the following example, the first locator's movement is confined to the x-axis and the ...
2k views

### How can I implement object oriented programming in Mathematica?

Roman Maeder's object oriented programming package is nice, but I'm hoping someone can suggest a sleek and novel implementation that is easy to use.
517 views

### 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 <...
825 views

### When to use Get vs Needs

When should I use << vs Needs? I just always use Needs as ...
1k views

### Passing large list by reference

I have the following problem: I would like to control evaluation of a variable that points to a list. For example, frequently in the code I have functions of the form that are supposed to work on ...
638 views

### How can you give a Module a context and have its local variables and Modules belong to that context?

What would be the best way to give a module its own context and have its local variables and Modules belong to that context?
807 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 ...
413 views

### How and when to use Evaluate?

A month ago, I used Mathematica to solve my experiment of the Test Technology of Mechanics Engineering. The exeriment is mainly about the Fourier Transform and verify the validity of the theory of ...
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 ...
479 views

### Function that caches when it returns unevaluated

How would you go about implementing a function that caches not the result but the fact that it didn't match a pattern? So that it doesn't waste time recomputing a complex time-consuming pattern ...
396 views

### Patternmatching sets

How to match set-patterns against sets? A set (in the mathematical sense) is a list of elements without repetition and order of elements does not matter. For example, we have a pattern set ...
848 views

### Is there anything like a C pointer (or returning a reference) in $Mathematica$?

I want to do in Mathematica what the following does in C. ...
805 views

### Modifying a List in a function in place [duplicate]

An example will be most specific: func[list_, column_] := list[[All, column]] = Map[#*2 &, list[[All, column]]]; This throws errors. I want to avoid doing ...
427 views

### How to efficiently Append a result of an operation on each element of a list to itself

I'm looking for the best function to apply the product of the last two elements of sublist elements to each element: Example: ...
1k views

### Populate an upper triangular matrix from a vector of elements

What is the best way to populate an upper triangular (or alternatively: lower triangular or symmetric) matrix from a vector of elements? This example input: ...
1k views

### optimization problem with NDSolve

I want to minimize the function fcc. When fcc is calculated for a specified point the answer is correct: ...
1k views

### Finding the square root of a random number with Newton's method, using While/Do/For loops?

I am trying to construct a program that will find the square root of a number, using Newton's method, which is $$x(n+1) = x_n- f(x) / f'(x_n)$$ The number, will be a random number, generated by: <...