An algorithm is a sequence of well-defined steps that defines in abstract the solution to a problem.

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17
votes
7answers
464 views

Faster position list construction from a “take instructions” list

Take some list, e.g., {1,2,3,4,5}, and a "take instructions" list, say {1,1,2,1,1}. The latter is read as "take the first ...
2
votes
2answers
33 views

Count elements between matching opening and closing parentheses?

Suppose I have a List of the form: lst={"(", "x1", "x2", "(", "(", "x3", ")", "x5", "(", "x6", ")", ")", ")"} For each pair ...
2
votes
2answers
71 views

Replace missing data

I have vectors of equal lengths where I want to replace the zeroes (missing data) with their preceding values. So far I have written: ...
8
votes
5answers
400 views

Match opening and closing parentheses?

Suppose I have a List of the form: lst={"(", "(", "(", ")", "(", ")", ")", ")"} By running ...
-4
votes
0answers
53 views

How convert code from C# to Mathematica [closed]

I must realize algorithm. I know how to write it on C# but I can't convert it into code in Mathematica. It is my code: ...
5
votes
1answer
278 views

How can I compute the chromatic index and number of a graph?

I saw a recent question from M.R. and realized there is no function to compute the chromatic index and number of a graph, other than a really slow method in the now deprecated Combinatorica. So, how ...
2
votes
1answer
71 views

Stochastic Predator-Prey model using Gillespie's SSA

I'm trying to model the predator-prey situation using SSA. I am very new to Mathematica so my handling of matrices is probably terrible, and that's probably adding to my confusion: ...
2
votes
1answer
86 views

Maximizing the number of zero entries in a matrix

I have a matrix with a bunch of parameters in its entries, they all come in different combinations in different places of the matrix. I can post the matrix itself if requested, but I think what I mean ...
0
votes
0answers
143 views

Spectral Clustering

I am interested in the following question: How is it possible to check whether an algorithm is working properly? However, this question is too general for the post and I'd like to restrict attention ...
2
votes
2answers
48 views

Efficiently or Elegantly construct linear graph list from vertex pairs

I am processing MRP data, with BOM relations as pairs of part number strings. I want to construct lists that represent the linear graphs defined by these pairs. Here is some code to generate random ...
1
vote
0answers
50 views

Implementation of Lubaehevsky-Stillinger Algorithm to pack hard spheres

To generate a model of a polycrystalline material with specified grain size distribution (e.g coming from a Monte Carlo Grain Growth simulation) the Paper "Effects of grain size distribution and ...
4
votes
1answer
54 views

Default algorithm in NonlinearModelFit

Does anyone know the default algorithm used in NonlinearModelFit? The documentation gives several possible algorithms, but I can't figure out what it uses if you do not specify the algorithm. Thanks. ...
0
votes
1answer
196 views

Code efficiency improvement needed solving problem 499 in Project Euler

I am trying to solve https://projecteuler.net/problem=499 by constructing a transition matrix and finding its steady state. Here is my code: ...
15
votes
7answers
581 views

Enumerating tuples from a larger space such that all pairs of values are present at least once

I am trying to write a function that will accept a list of N lists and returns a list of N-tuples that represent all pairs of values from the original N lists at least once. To illustrate with an ...
1
vote
0answers
71 views

How can I detect certain letters by shape in an image?

I have a website where people can post Flipbook animations, called Flipnotes. Unfortunately, most of the Popular flipnotes are in the following categories: MV (Music Video) AV (Audio Video) AMV ...
0
votes
0answers
78 views

How to recursively check is a graph is a binary search tree?

I'm having trouble using the built in DepthFirstScan[] to see if a tree satisfies the binary search tree property, the documentation is confusing. Motivation: I'm ...
2
votes
0answers
42 views

How to compute the longest non-contiguous common sequence?

LongestCommonSequence[] works well, but what about finding the longest common sub-sequence (not necessarily contiguous)? Is this function built in to the genome ...
0
votes
0answers
44 views

Independent Set Sorting

Let's say I have a graph g, and I wanted the largest independent vertex set of g. I would write then, ...
14
votes
3answers
172 views

Partitioning with constraints on subsets

Given the following data: constraints = {{11, 2}, {11, 3}, {11, 4}, {11, 6}, {11, 9}, {1, 6}, {5, 6}, {2, 5}}; weights = {3, 7, 3, 2, 4, 2, 2, 2, 3, 2, 1}; I ...
4
votes
1answer
204 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 ...
5
votes
2answers
301 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 ...
3
votes
1answer
117 views

How to execute a notebook in background

I am developing an algorithm that take time to return results. I thought if I could run this notebook in background and continue to develop the rest of my work. It is possible to do that?
7
votes
1answer
153 views

How to know the internal algorithms of functions like Predict or Classify?

The document centre seems only explain how to use these functions, but just in an very brief way. I know Mathmatica is not open source, so we can not expect to see the code of the function, but are ...
4
votes
0answers
88 views

Implement a piecewise function elegantly and efficiently

Given that $$ g(x)= \begin{cases} max(x_{min},x-m) & 0.5x \leq max(x_{min},x-m) \\ 0.5x & max(x_{min},x-m)<0.5x<min(1,x+m) \\ min(1,x+m) & min(1,x+m)\leq 0.5x \end{cases}$$ ...
0
votes
1answer
52 views

timing series algorithm [closed]

If we have a timing series t1,t2,t3.... and every timing point means an event. A time interval T is given. Once T is given, how to calculate the maximum event number happening in T? case A ...
22
votes
7answers
668 views

Alternative ways to implement a triangular recursion

Triangular recursions are a class of algorithms that frequently turn up in computational mathematics. These recursions are expressible in the general form ...
6
votes
3answers
280 views

Calculating integral by Romberg Algorithm

In my "Numeric Anasyis" course, I learned the Romberg Alogrithm to calculate the numerical integral. The Romberg Alogrithm as shown below: $$ ...
3
votes
3answers
80 views

Generating increasingly longer lists from a single list

I start with an array such as {{1,1},{0,1},{-1,1}}. (1) I want to create an array from this which replaces each array inside the array with 3 new arrays, one ...
6
votes
2answers
357 views

Pruning elements in an array based on the existence of similar elements in adjacent arrays

Imagine I have a series of particles floating around in $\mathrm{R}^3$, where, at any given time, particles can pop into and out of existence. Here, for some number of time points, $(t_1, \dots, ...
2
votes
1answer
180 views

How to create a Poincare disk type kaleidoscope in Mathematica?

Creating a Kaleidoscope in Mathematica is not a new topic at all, examples can be found from the links like: Wolfram reference and Wolfram demonstrations. My question is how to create Poincare disk ...
2
votes
1answer
134 views

Neighbourhood - Calculations

SeedRandom[0]; n = 5; (m = N @ RandomInteger[{1, 3}, {n, n}]) // MatrixForm result1 = MeanFilter[m, 1] // MatrixForm ...
49
votes
3answers
23k views

How to create a new “person curve”?

Wolfram|Alpha has a whole collection¹ of parametric curves that create images of famous people. To see them, enter WolframAlpha["person curve"] into a Mathematica ...
10
votes
5answers
665 views

How to deal with recursion formula in Mathematica?

In engineering problems, I am always seeing many recursion formula. For instance, In the book "The NURBS book", I discovered many recursion formula Fibonacci ...
2
votes
3answers
443 views

computing gaussian curvature

Can gaussian curvature K be computed from WolframAlpha or any other available Mathematica ...
10
votes
2answers
201 views

Temporal database reconstruction in mathematica

<EDIT> after some internet research I found the database domain that deals with this kind of thing: Temporal Databases. I think my question therefore becomes how to reconstruct a temporal ...
2
votes
3answers
62 views

Reconstructing an expression [duplicate]

I have a nested expression like this one expr = Tan[Sin[Cos[x]]]; I can deconstruct it with ...
3
votes
2answers
216 views

A problem about recursion formula of deCasteljau algorithm

I use mathematica to realize the deCasteljaul algorithm $$\vec{P}_{k,i}(u_0)=(1-u_0)\vec{P}_{k-1,i}(u_0)+u_0\vec{P}_{k-1,i+1}(u_0)$$ The graphics that deCasteljaul algorithm generated as below: ...
5
votes
2answers
160 views

Graph expansion on Mathematica

Is there a way by which Mathematica can be given a graph as an input and be asked to find its expansion? Note: By "expansion" I mean the quantity called "isoperimetric number" or "Cheeger constant", ...
8
votes
3answers
300 views

Random Integer Sequences

I want to construct a random square matrix in the following manner: a) Three states [0 | 1 | 2] are repeated ...
14
votes
2answers
421 views

Better way to test that a matrix is upper-triangular?

Today, I got to thinking about how to test that a matrix was upper-triangular. So I had a try at it. Algorithm $\quad \quad a_{ij}=0 $ Or $i \leq j$ $\Rightarrow$ $True$ My solution is ...
9
votes
3answers
910 views

An inverted pyramid

I want to draw a pyramid approximately like this ...
11
votes
7answers
647 views

Splitting strings into letter keys and integers

I have strings of the following form: string = "ABC123DEFG456HI89UZXX1"; Letter keys of variable lengths are followed by (positive) integers. I want to get this ...
9
votes
5answers
709 views

Coalition Games

Suppose an election produces the following result: result = {{"a", 120}, {"b", 80}, {"c", 50}, {"d", 30}}; Letters are parties and numbers seats. To form a ...
18
votes
3answers
439 views

How to generate a blank crossword sheet?

I attempted to generate a blank crossword sheet. My method is by combining the rows and columns as shown on the graph below. However, some of the across and ...
9
votes
4answers
298 views

Replacing matrix values

I want to find the n largest values in a matrix and replace all others with zero. The solution I found uses ReplaceAll and becomes very slow as the size of ...
9
votes
2answers
196 views

Extracting values with multiple keys

I want to extract sorted data from a huge database based upon two (or more) keys in a very timely manner. Here is a reproducible toy example for two keys only: ...
4
votes
1answer
127 views

How to make a case insensitive sorted list and rename the file names of a given folder?

Suppose I had about 500 .JPG and .jpg files in my folder "c:\images\". How to ask ...
0
votes
6answers
218 views

How to build a game board [duplicate]

I have - rather lazily - constructed a chessboard like this: ...
12
votes
2answers
445 views

Implementing an algorithm for finding the largest circle that contains a single point in a set (and no other point)

This question concerns the implementation of an algorithm proposed by Rahul Narain on a former question of mine that was migrated to math.stackexchange: ...