Questions tagged [algorithm]
Questions about algorithms used or which might be used to implement a procedure known by name or loosely but not in detail. The subject of the question may be a procedure mentioned in the literature or a Mathematica built-in function
11
votes
2answers
738 views
Solving “Resistance between two nodes on a grid” problem in Mathematica
In the context of resistor networks and finding the (equivalent) resistance between two arbitrary nodes, I am trying to learn how to write
a generic approach in Mathematica, generic as in an approach ...
0
votes
0answers
63 views
Most efficient way to define evil and odious numbers [duplicate]
A positive integer $n$ is defined to be evil if the number of ones in its binary expansion is even, otherwise it is odious. Now define the function
$$
\begin{equation*}
t(n)=
\begin{cases}
1 \rm{ \...
1
vote
0answers
74 views
How can I improve and accelerate my 2 D algorithm?
I implemented the algorithm descussed here in the 1 D case (when $g$ is one variable function). Using a relaxation parameter the algorithm became very fast and converges in few iterations (n = 5, 6, , ...
4
votes
1answer
169 views
Finding the dangling free part of a percolating cluster
I am trying to learn how to use Mathematica for analyzing graphs, more specifically in the context of connectivity and percolation.
The graph is embedded in a 3d cubic box of a given length, the ...
3
votes
0answers
67 views
Approximate Nearest Neighbors in Mathematica?
Is there any support for Approximate Nearest Neighbors (ANN) in Mathematica or third-party packages? I'm looking for a good implementation of locality sensitive hashing for applications where ...
3
votes
0answers
73 views
Hopcroft's Algorithm for Minimization of Deterministic Finite State Automaton
Background
Given a deterministic finite state automaton, Hopcroft's algorithm is a $O(n \log(n))$ algorithm for finding an automaton that generates the same language with a minimal number of vertices....
2
votes
0answers
24 views
How to iterate over Orbit of PermutationGroup?
Another day, another permutation group question.
I'm given a g=PermutationGroup[...], and a list l={1, 3, 3, 2, ...}. I know I ...
1
vote
0answers
55 views
Trying to compute the heat capacity for the 2D-Ising model
I'm trying compute the heat capacity $C_v$ out of my simulation for the 2D-Ising model which is given by
$C_v = \frac{\langle E^2 \rangle - \langle E \rangle^2}{T^2N^2}$ ($E$: Energy, $T$: ...
1
vote
1answer
62 views
Defining iterative algorithms [closed]
Assume the iterative algorithm of interest to be as follows:
...
4
votes
1answer
48 views
Mathematica package to calculate the graph crossing number
I have been searching for a mathematica package that can calculate the graph Crossing number of a (small) given arbitrary graph (the graphdata of known graphs doesn't help me). Before I write my own ...
1
vote
0answers
68 views
How can we make an algorithm with the A* method in Mathematica with 5 different flight routes? [duplicate]
I need to find the shortest path with the A* algorithm using Mathematica.
I have 5 different flight routes with coordinates. They start and end at the same point. Between every point there is a wind ...
2
votes
3answers
82 views
How can I compute the chromatic number of a graph?
I'm starting in Wolfram Mathematica.
I saw that MinimumVertexColoring [g] could be used to calculate the chromatic number of a graph, but ...
3
votes
1answer
105 views
Identify emotions from a drawn face using machine learning?
Can someone tell me how you could modify this code so that it recognizes more facial expressions? ... thanks for the help.
...
6
votes
1answer
450 views
Which algorithm does Mathematica use for “RandomSearch”?
Recently I have used Mathematica for minimization of certain functions and I have realized that even though it lasts much longer, the method "RandomSearch" functions much better than the other methods ...
4
votes
1answer
229 views
Pythagorean quadruples
I am very interested in the problem that deals with the Pythagorean quadrruples, which are listed in rosettacode. Unfortunately, I have not been able to find any way to compute them with Mathematica. ...
7
votes
1answer
341 views
Why is SVM unable to separate linearly separable data?
I have two sets of data, namely blue and yellow. I manually added a point {8, -3} to the blue data.
...
3
votes
0answers
141 views
How to achieve with Mathematica the effect a closure has in other languages?
Motivation
I want to write an auxiliary function (brief auxf) for testing the output of another function that evaluates its body repeatedly using ...
3
votes
1answer
107 views
How to improve the simulation speed?
I'm new here. Actually, Mathematica is so cool, I can just write about 5 lines to do the same thing comparing to over 100 lines in Python. But the speed is very slow. I wonder if there is any method ...
7
votes
2answers
147 views
Generating permutations
I have a list of different combinations of letters of the alphabet
{{"a"}, {"b"}, {"c"}, {"a", "b"}, {"a", "c"}, {"b", "c"}}
There is no pattern to them - that ...
0
votes
2answers
69 views
An Integrate result is not what it should be
Recently, I come across an algorithm called HyperLogLog (https://stackoverflow.com/questions/12327004/how-does-the-hyperloglog-algorithm-work). There's a magic number in it, and when reading the paper,...
10
votes
1answer
178 views
Quick QuickSort implementation
I am playing with julialang and loving it, but at the same time noticed that they have a benchmark comparison with Mathematica. I have already submited a better version of ...
3
votes
1answer
75 views
What algorithm is used by FindGeometricTransform? [closed]
Can anyone tell me how the operation FindGeometricTransform[pts1, pts2] works (I mean inside logic of the transformation function), or where can I find such an ...
5
votes
2answers
134 views
How to mark leaves of polynomial based on its position in tree
I've been struggling with this for a few days, and so I thought I might ask this here. Part of the problem lies in the fact that I do not even know the mathematical solution, which runs the risk of ...
1
vote
1answer
174 views
Find a few eigenvalues of a HUGE sparse Hermitian matrix
I know that methods such as Arnoldi and FEAST can be employed to only find a few eigenvalues. But now I need to add another ...
1
vote
3answers
78 views
0
votes
1answer
168 views
Using the binary search algorithm in a sorted grid
I want to get a mathematica code for binary search algorithm applied to a sorted grid containing integers.
For example, given
f[k_,x_]= x^2 + k x + k - 2
where <...
0
votes
0answers
71 views
What method Mathematica uses to solve a quadratic system
I'am writing a paper and I need to know what method Mathematica uses to solve a quadratic system by default.
This is my system:
...
6
votes
2answers
556 views
How to calculate the “center” point
I have such points
pts = Uncompress[FromCharacterCode[
Flatten[ImageData[Import["http://i.stack.imgur.com/zEP05.png"],"Byte"]]]];
ListPlot[pts]
If I use the ...
3
votes
3answers
2k views
Algorithm too slow
Writing:
nn = 10;
Table[Sum[Length[Select[DeleteDuplicates[Map[Sort, Tuples[
{1, 2, 5, 10}, i]]], Total[#] == n &]], {i, 1, n}], {n, 1, nn}]
I get:
{...
0
votes
0answers
30 views
Using space to denote multiplication [duplicate]
When I want to impress a Mathematica novice I show him how we can use spaces to denote multiplication (telling him also to be careful not to forget the space as in ...
6
votes
2answers
302 views
Improve my implementation of the Diamond square algorithm
Some time ago, I began to explore the magnificent world of the terrain generation using the computer. Investigating on the Internet know about the existence of the diamond square algorithm. Try to ...
4
votes
1answer
177 views
solid partitions generator
According to Wikipedia, a solid partition of $n$ is a three-dimensional array $n_{i,j,k}$ of non-negative integers (with indices $i,j,k \geq 1$) such that $$\sum_{i,j,k} n_{i,j,k}=n$$ and $$n_{i+1,j,k}...
3
votes
1answer
263 views
Metropolis-Hastings Algorithm Problem
I've been trying to implement the Metropolis-Hastings algorithm for a while but there seems to be something weird going on.
This algorithm does not need as much of the statistics to understand, and ...
6
votes
4answers
408 views
How to speed up this high-dimensional definite integral?
Examples
➤ 1.
$$I=\iiint\limits_D \dfrac{{\rm d}x\ \!{\rm d}y\ \!{\rm d}z}{(x+y+z)^p}~,$$
where
$$D=\{~(x,y,z)~\colon~x>0~,y>0~,z>0~,x+y+z<1~\}~.$$
MMA gives: $~I=-\dfrac1{2(p-3)}~.$
➤...
2
votes
2answers
89 views
I want to improve my algorithm of knowing eigenvalues of the matrix H(k)
I want to improve my algorithm.
I want to know the eigenvalues of below n-dimensional matrix H. When n=10, the matrix H is like below.
Now, $To$ and $M$ are constants and $T1$ and $T2$ are functions ...
4
votes
2answers
197 views
Numerical Join of two sets of vectors ignoring repeats
I have two sets of numerical vectors which can be either Real or Complex and I want to combine them together, ignoring repeats.
...
2
votes
1answer
175 views
How to visualize elastic collision among particles confined in a square 2D container?
I've already simulate two particle confined in a square 2D container, but I don't know how to simulate the elastic collision between them. Currently, they just pass through each other without any ...
1
vote
1answer
151 views
Creating subsets of lists of lists which have certain properties
PREFACE:
This question is about a proper algorithm and its implementation. I will explain the problem as detailed as possible and will give my current algorithm as well as two more possible solutions ...
1
vote
2answers
306 views
How to convert from C to Mathematica?
I am trying to understand what is explained in this webpage, in the section entitled "Generating noise with different power spectra laws". After reading that section, I thought I could do it in ...
2
votes
1answer
101 views
3D binning keeping the values
I have N points in the from of triplets {xi,yi,zi}.
I would like to bin them on a grid ...
0
votes
2answers
146 views
Testing that an algorithm has converged
It's frequent that when writing some kind of algorithm (numerical integration, clustering, whathaveyou) I'll want to say "Stop the algorithm and return the result when some error $\epsilon$ is below ...
1
vote
1answer
318 views
Allan Deviation Algorithm
I am trying to write my own Allan Deviation calculator in Mathematica using the definition,
$$\sigma(\tau)^{2}=\frac{1}{2M-2}\sum_{i=1}^{N-1}(\bar{y}_{i+1} - \bar{y}_{i})^{2}\text{.}$$
Where the $\bar{...
11
votes
1answer
481 views
3D tree in Mathematica?
Searching the web for information about the affine transformation, I found the one page, which called my attention for the tree that show and is this
but unfortunately do not give information about ...
1
vote
0answers
57 views
Finding same output values by varying input values of function
I have written a function in Mathematica that needs five input variables.
The function outputs a single real number. The underlying model is a complex model for option pricing. To ease things up, let ...
8
votes
3answers
277 views
From a list of lists of integer, choose a minimal length list of integers that intersects each sublist
I have this list of lists of integers between 1 and 255.
...
4
votes
0answers
245 views
Problem with the accuracy of the real-coded Genetic algorithm
Since there is no Genetic algorithm implemented in the Mathematica i tried to write a very simple genetic algorithm myself. The accuracy of the results depend upon rounding up the obtained parameters. ...
-1
votes
1answer
58 views
While condition
I have the following code:
While[Total[{0,1,3}] != 2,
{0,1,3} -(#[[Ordering[Max[] & /@ #]]])]
I want to decrease the maximum coefficient of the vector ...
17
votes
3answers
796 views
Image segmentation by pixel value
I'm looking for a way to segment a grayscale image (or a 2D array) by its pixel values. We look at two neighboring pixels, if their values are close within a certain threshold, then we say they are ...
2
votes
0answers
44 views
Dean's apportionment
I would like to program Dean's apportionment. https://www.maa.org/press/periodicals/convergence/apportioning-representatives-in-the-united-states-congress-deans-method-of-apportionment
Here is my ...
0
votes
0answers
69 views
Algorithm that will trim a unique ID number and produce a shorter unique ID
I have a unique ID number with 2^128 magnitude length (128 bits). This means ~3.4e+38 which is quite large that my actually needs, spending valuable time in a transmission protocol.
There is a ...
