Stack Exchange Network

Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

Questions tagged [algorithms]

An unambiguous list of computational steps involved in finding a solution to a class of problems.

3
votes
2answers
33 views

How do I check the validity of a set of inequality constraints? [closed]

I have a table of inequality constraints, each with an "x < y" relation. How can I check this table for contradictory logic such as a < b, b < c, c < a? For example ...
2
votes
2answers
139 views

The Universal Approximation Theorem vs. The No Free Lunch Theorem: What's the caveat?

The universal approximation theorem: A neural network with 3 layers and suitably chosen activation functions can any approximate continuous function on compact subsets of $R^n$. The no free ...
2
votes
2answers
76 views

Is there a clustering algorithm that maximizes average silhouette? If not, why not?

The average silhouette index of a clustering of data seems to be used to determine the hyper parameter $k$ (i.e. number of clusters) in clustering algorithms like $k$-means. Is there an algorithm that ...
2
votes
0answers
16 views

What are the simple methods to do an unsupervised cluster to stock return time series?

I am a student in finance and I am working on my thesis project. I am interested in doing a clustering to stock time series. I first read the paper 'Time-series clustering – A decade review' from ...
0
votes
0answers
10 views

Prediction problem- Build model using 6 months data and predict on one month data?

I have a data set which contains site usage behavior of users over a period of six months. It contains data about: Number of pages viewed Number of unique cookies associated with each user Different ...
0
votes
0answers
20 views

Optimizing a sequence of events on a variable conditional on the event

I'm trying to understand how I would approach a problem aiming to optimize a sequence of events to maximize another variable. For example, say I start selling a t-shirt at multiple stores, where each ...
1
vote
0answers
44 views

Optimal Sequence Problem

Lets says I have 100 people that like to buy item x. They ask me to send them a message every time I have x available to sell. Of the 100 people that like to buy item x: 1) Some people will pay more ...
0
votes
0answers
6 views

Grouping by equivalent path length

I have a collection of an arbitrary number of discrete "path lengths". I'm interested in discovering some automated (preferably Excel or C++/C#/Java code rather than Matlab or similar) method of ...
2
votes
0answers
48 views

Efficient linear regression given columns of A rather than rows of A

I'm analyzing a large problem with a large $N \times M$ data matrix $A$, where $N$ is the number of observations, $M$ is the number of explanatory variables, and $N \gg M$. I'd like to perform single-...
1
vote
1answer
31 views

How can I use patterns from data analysis to make a predictive machine learning model?

I'm trying to make a predictive model that can predict how well a product will sell in the future based on certain parameters. I've made some visualizations showing the relationship between the data. ...
1
vote
1answer
74 views

What are some good canned classifiers for high-dimensional data with probablistic labels, besides neural nets?

I've got a classification problem where my labels are $N\times4$ matrices of probabilities of class membership, and I've got about 1800 covariates. The covariates are mostly granular, in the sense ...
0
votes
1answer
37 views

Cross Validation in application of clustering on a collection of similarly behaving time series

I'm trying to understand how and at which point can one apply Cross Validation for time series data. If i'm not wrong CV increases generalisation so that our model has less bias in case the data is ...
0
votes
0answers
10 views

Multivariate fixed point iteration: the wrt variable on both sides of update equation and not are different?

I try to understand more about the update in multivariate fixed point iteration. I saw the examples where the updates have the same variable (the wrt. variable of partial differentiation) on both ...
0
votes
0answers
18 views

Optimize function on two stages

I have a non-linear cost function (which I do not know its analytical derivative and it is pretty hard to be computed). The function takes 8 parameters. I need to minimize this function using some ...
0
votes
1answer
42 views

Given list symptoms and diseases - how to find similar symptoms based on data

I have a dataset of case studies like that: Gender ; Age ; Symptom ; Condition M ; 20 ; Fever ; Flu F ; 29 ; Arm pain ; Trauma F ; 40 ; Fever ; Cancer M ; 90 ; ...
4
votes
2answers
60 views

Is there an algorithm for listing all/minimum admissable sets in a graph that satisfies the backdoor criterion in Causal Inference?

I would like to know if there exists an algorithm for finding all/minimum admissible sets in a graph that satisfy the backdoor criterion as defined by Judea Pearl in his book Causality (Please see ...
1
vote
1answer
39 views

Algorithm for selecting largest possible value, when observing online sequence of unknown distribution?

I have been trying to devise an algorithm for a problem that's been bugging me for a while. For some weird reason I haven't been able to find any mention of this problem in the literature, so far. I ...
3
votes
1answer
67 views

Is there a (matrix) operation that can count elements in vector pairs?

For two vectors $x \in \{0, 1, 2\}^{n}$ and $y \in \{0, 1, 2\}^{n},$ I need to generate a matrix $C\in \mathcal{R}^{3\times3}$ where $C_{i,j}$ equals the number of indexes $t$ where $x[t]=i$ and $y[t]...
0
votes
1answer
110 views

Difference between Hartigan & Wong Algo to Lloyd's algorithm in K-means clustering

In the iterations of Hartigan and Wong Algo of K-Means clustering, If the centroid is updated in the last step, for each data point included, the within- cluster sum of squares for each data point if ...
1
vote
0answers
22 views

best statistical approach to study the time evolution of clustering in a data set

I am using a stochastic method for the clustering of a data set. The number of clusters that this approach returns, can differ in each iteration. On the other hand, I would like to study the evolution ...
1
vote
1answer
152 views

Arithmetic operations on Random Variables [closed]

Firstly, I do not have statistics background other than a single lesson I took more than a decade ago, so I will use incorrect terms to explain my question. And probably it is one of the reasons that ...
-2
votes
2answers
91 views

Which clustering algorithm to use for dataset with high variance

I am working on an unsupervised learning problem and can use a little help for the same! Objective: To find out significant payment patterns or segments of customer who tend to have similar payment ...
0
votes
2answers
66 views

Optimization algorithm where calculating the function is very costly [duplicate]

I am doing physics simulation and have to minimize a function $f$ of approx. 10 parameters $f=f(x_1, x_2, ... , x_{10} )$. I have already looked into several optimization algorithms (downhill-simplex, ...
0
votes
0answers
33 views

Sample covariance matrix notation

I do not understand this notation for the sample covariance matrix (from Artificial Intelligence: A Modern Approach, Peter Norvig and Stuart J. Russell, Section 20.3, EM algorithm): $\Sigma_{i} = \...
4
votes
1answer
149 views

What is a good algorithm to match the class distribution of two data sets?

I have data generated by a Monte Carlo simulation (let's call it MC) and a second data set (let's call it data), each having events in two classes 0 and 1. I am trying to write an algorithm such that ...
2
votes
0answers
115 views

Vapnik-Chervonenkis Dimension

My question has to do with the VC dimension of the class of convex polygons with $m$ vertices. A solution to this problem is given in the following: Advanced Algorithms. Call the class of all ...
0
votes
1answer
33 views

General form of a machine learning algorithm

This is the general function that represent any machine learning algorithm: $Y=f(X)+\epsilon$ , where $Y$ is the dependent variable, $X$ is the independent variable and $\epsilon$ is the random error ...
1
vote
0answers
46 views

Logistic regression on HDFS, what's the algorithm?

How does Spark (or something similar) estimate a logistic regression model, or any statistical model that is estimated by an optimization algorithm, when the data are stored in a distributed ...
2
votes
1answer
72 views

Detect visual attention area in an image [closed]

I'm trying to detect the visual attention area in a given image and crop the image into that area. For instance, given an image of any size and a rectangle of say LxW dimension as an input, I would ...
6
votes
0answers
117 views

Good choices of PRNG for uniform circular (directional) data?

I'm planning to simulate iid one-dim variates with continuous uniform distribution on a normalized circle (which circumference is $1$ instead of $2\pi$). Namely, a sample consists of $n$ points ...
0
votes
0answers
107 views

Applications of FFT algorithm in statistics? [duplicate]

Are there any applications of the FFT algorithm in basic statistics i.e.: estimating a density distribution? I would like to learn more about it - and it would be nice to work on an actual example ...
0
votes
0answers
21 views

Markov Chain Monte Carlo [duplicate]

what are the differences between M-H algorithm and M-H-within-Gibbs algorithm. If possible, upload for me the two algorithms please.
4
votes
2answers
119 views

Is it possible to train a machine learning model to predict the next prime number?

As there are no patterns to prime numbers. Is there any way in which ML could predict it?
2
votes
1answer
54 views

What algorithm to use to predict customer count given past data?

I want to predict the number of customers on an hourly basis in a store given its previous data regarding how many customers came in the store per hour. The prediction would look like something below: ...
1
vote
0answers
43 views

Web Content Partial matching algorithm suggestions?

I am trying to find a word or set of words or a similar word in the new web page scraped from publicly available sources to answer a question. I have a small list of keywords against which I would ...
0
votes
0answers
36 views

Given a query image Q and two other images X and Y, how to determine which one is most similar to Q?

Given a query image Q and two other images X and Y (you can assume they have more or less the same resolutions if that simplifies the problem), which algorithm would perform extremely well at ...
0
votes
0answers
29 views

Multistage sampling in R. Only final sampling size given

I am trying to implement an algorithm for sampling in several stages where only the final size of the sample is known. Here is an example of the structure of my sampling frame. Where: cluster is a ...
0
votes
0answers
39 views

Mathematical characterization of a dataset (only one class is always predicted)

I have a dataset (~ 30K records) for binary classification. The dataset has both positive and negative examples (65%-35%). Though I do not claim that I have exhausted all the possibilities, still it ...
0
votes
0answers
7 views

R: Algorithm to create groups with cohesion [duplicate]

I don't know if this belongs here, but anyway, here's my doubt. I have a 52x52 matrix with the distances between each pair of 52 points. I want to create an algorithm that classifies them into a ...
0
votes
0answers
19 views

Algorithm for creation of groups with cohesion

I don't know if this belongs here, but anyway, here's my doubt. I have a 52x52 matrix with the distances between each pair of 52 points. I want to create an algorithm that classifies them into a ...
1
vote
0answers
91 views

In a neural network, how are weights adjusted between the third to last and second to last layer of neurons?

I haven't been able to find much information that explains back propagation in simple terms. I would like to know what is happening (what is the algorithm) to be able to code one in java. I know that ...
1
vote
1answer
88 views
1
vote
0answers
46 views

Which machine learning methods include convex maximization? [closed]

As far as I know, maximizing a convex function (or minimizing a concave function) is an NP-hard problem even with linear constraints. Which machine learning methods include such a setting? Can we ...
0
votes
0answers
13 views

How to optimize activity scheduling with dependencies and resource requirement?

I have a list of activities $A=[a_1 \cdots a_n]$. Each activity has a duration $d$ and a resource demand $r$. The resource availability varies over time. Moreover, each activity may have a ...
22
votes
4answers
2k views

Textbook on the *theory* of neural nets/ML algorithms?

Every textbook I've seen so far describes ML algorithms and how to implement them. Is there also a textbook that builds theorems and proofs for the behaviour of those algorithms? e.g. stating that ...
1
vote
2answers
302 views

Why the EM algorithm instead of a more direct computation? [duplicate]

Assume we have a probability distribution $P(y,z|\theta)$, where $x$ is the total set of variables divided into observable variables $y$ and hidden variables $z$, and data on observable variables $y$. ...
1
vote
0answers
115 views

Simplistic Write-Up of XGBoost Algorithm

I was wondering whether anybody could check through my very simplistic (e.g., no detail of greedy split finding algorithm) write-up of the XGBoost algorithm for binary classification. Algorithm: ...
0
votes
0answers
331 views

Where could I find pseudocode for XGBoost?

I was wondering whether anybody knew where I could find pseudocode for the XGBoost algorithm?
1
vote
1answer
82 views

Can the Louvain Modularity algorithm create communities of unconnected nodes?

I have an implementation of Louvain that is creating communities with unconnected nodes. I want to know if I am doing Louvain wrong or if this is possible in a correct implementation of Louvain? ...
1
vote
1answer
62 views

Calculating variance of distribution when given various sums of that distribution

I have a distribution $X$ with an unknown mean and variance. I wish to calculate its variance, but all I am given is an infinite series of data points $(y_i, n_i)$ of the form: $$y_i = \sum_{n_i} x$$ ...