Stack Exchange Network

Stack Exchange network consists of 174 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.

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
112 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
70 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
64 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
31 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
143 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
104 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
32 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 ...
0
votes
0answers
35 views

What´s the best way to compare 2 ranked lists among the same dataset. (health informatics)

I´m working in an algorithm that weights coded health problems in electronic health records of single patients. I´ll create a gold standard of the ranking (namely: heart faliure>diabetes>hypertension>....
1
vote
0answers
45 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
70 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 ...
5
votes
0answers
107 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
83 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
114 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?
0
votes
0answers
49 views

Examples of machine learning algorithms where it is not recommended to scale/normalise/mask the data?

We need to share company internal data with a vendor. In order to protect sensitive data, we have masked personal information such as customer id etc. We are discussing the pros and cons if we should ...
2
votes
1answer
50 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
39 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
33 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
26 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
17 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
77 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
79 views
1
vote
0answers
43 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
12 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
216 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
93 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
266 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
60 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: $$y_i = \sum_{n_i} x$$ ...
1
vote
2answers
46 views

calculating distance to 1 (positive and negative numbers)

I have what I assume is a very simple question. I have a range of numbers from 81 to -6, that corresponds to racios pop. growth/urban construction of cities. The ideal ratio would be = 1. I need, ...
0
votes
0answers
245 views

What are differences between K-means versions: Lloyd, Forgy, Macquen, Hartigan and other?

I'm looking for the (perhaps brief) explanation of the main differences between the different K-means clustering procedures, such as between Lloyd, Forgy, MacQueen and Hartigan, and possibly other ...
1
vote
0answers
101 views

Algorithm for nested bootstrap resampling of (X,Y) pairs in multiple linear regression

I'm writing up a procedure I used for meta-analyzing an experimental data set. My objective is to come up with a formalization that is clearly replicable. I used the bootstrap to sample observations (...
0
votes
0answers
30 views

Predicting median revenue: What are some good methods to look into for this forecasting problem?

I am currently working on a project involving prediction using machine learning. My data consists of taxi details from a city: such as cab ID, time stamp, start and destination locations, total price ...
7
votes
1answer
77 views

sampling cost of $O(d)$ versus $O(2^d)$

I came across the following simulation problem: given a set $\{\omega_1,\ldots,\omega_d\}$ of known real numbers, a distribution on $\{-1,1\}^d$ is defined by $$\mathbb{P}(X=(x_1,\ldots,x_d))\propto (...
0
votes
0answers
16 views

What algorithm to use to classify users based on collected metrics and a set of rules?

I have a data set that contains in-game players actions and interactions (stored as metrics). I want to create a recognition system that contains a set of predefined rules and takes as inputs the ...
0
votes
0answers
19 views

How do I make compatible the data types in your dataset with the input specifications of different machine learning algorithms?

Many times I read: "Majority of machine learning algorithms work with numbers, so you can to transform your categorical values and string into numbers." But then I wonder what happens with ...
0
votes
0answers
13 views

If algorithm is derived from majorization-minimization, is it correct to measure error from the majorized form?

The main objective function I wish to use for my algorithm is Kullback-Leibler divergence which can be majorized as: $D(V ||WH) \leq -\sum_{ij} V_{ij} \sum_{k} \pi_{ijk} log W_{ik} H_{kj} + \sum_{ij}(...
1
vote
0answers
52 views

Bishop: EM algorithm, expectation step [duplicate]

I am reading the Bishop Pattern Recognition and Machine Learning and am on section 9.3 An Alternative View on EM: I am confused as to how Bishop obtains the expression $Q(\theta, \theta^{old}) = \...
0
votes
0answers
30 views

What are some popular destination ranking/popularity algorithms?

I am trying to find examples of algorithms that rank certain items (for example destination cities) based on historic data. This data includes things like number of searches and conversion rates as ...
0
votes
0answers
54 views

ADAM Gradient descent oscillates close to minimum

I am using ADAM as an optimization algorithm to minimize some black box function $f(x,y)$. I know this function is convex and has a minimum $f(5,5) = 0$. Initially, the algorithm proceeds as expected:...
0
votes
0answers
7 views

Why does pre-initializtion matrix with priors for algorithm help it run faster?

I am quite sure that pre-initialization with right prior knowledge for algorithm should help algorithm run faster (and probably easier for cost function minimization?). I also run my algorithm (NMF) ...
1
vote
0answers
72 views

Auto Differentiation in Deep Learning Libraries

It is said that auto-diff is very efficient in generating the derivatives for backpropagation algorithms. The why is it that some of the most widely used deep learning libraries like Theano and ...
0
votes
0answers
31 views

What is the optimal gradient descent variation for a smooth function with clear minimum?

I can implement a vanilla gradient descent alogrithm, to minimize some function $f(x,y)$. Now if I know a priori that this function is smooth with a single global minimum (i.e. no local minima for a ...
1
vote
1answer
98 views

Designing a simple Reinforcement Learning themed game?

So I'm trying to write a (super) simple RL based game, where the agent is on the ground and has to evade obstacles falling from the sky. Based on what I've read about RL, I thought it would be a ...
0
votes
0answers
14 views

How to tune memory updation method in Harmony Search Algorithm for solving Bin packing problem?

I am trying to solving bin packing problem using using Harmony Search Algorithm but I am not able to find satisfactory results. Which are the crucial parts in Harmony Search Algorithm which I need to ...
0
votes
0answers
19 views

Using machine learning to predict entities

Im curious about an approach, since i start with machine learn a few months i wonder whats the best algorthm or approach to solve that: imagine that i have a entity like this: ...