# Questions tagged [classification]

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### A text-classifier that explains its decisions

I am building a text categorizer for short sentences. In addition to telling the user "the category of the text you entered is C", I want to be able to explain why I made this decision, in a short ...
1k views

### When should I move beyond k nearest neighbour

For many machine learning projects that we do, we start with the k Nearest Neighbour classifier. This is an ideal starting classifier as we usually have sufficient time to calculate all distances and ...
22k views

### Size of decision tree and depth of decision tree

I'm doing some classification experiments with decision trees ( specifically rpart package in R). By setting the depth of a decision tree to 10 I expect to get a small tree but it is in fact quite ...
1k views

### Algorithm to find a line that divides the number of points equally

I have recently been asked in an interview to devise an algorithm that divides a set of points in a coordinate system so that half of the points lie on one side of the line, and the rest on the other ...
1k views

### What machine learning method for diabetes prediction SW?

I'm thinking of an application for diabetics, that, given previous values of blood glucose and insulin dosage, predicts the glucose level for the next few hours. I know a few things about neural ...
435 views

### Theory of multi-label classification

Multi-label classification is a machine-learning problem where each sample can have zero or more labels from a closed set of possible labels. This task has applications in several fields. For example, ...
4k views

### Word classification algorithms

I am looking for algorithms to classify words in a paragraph of text. I am particularly interested in a classification to determine if a certain word is noun, verb, etc., but also looking for any kind ...
59 views

### Given $k$ points in $n$-dimensions, such that $n\geq3$, is there a polytime algorithm for finding a curve that splits them into 2 sets of points?

So in this math exchange question I asked, it was proven that for $n>2$ dimensions, you can always find a curve that separates $k$ points in $n$-dimensional space into $2$ arbitrary sets that you ...
251 views

### What is a good approach to symbol identification/recognition given a path, instead of raster data

Excuse any mistakes in my description as I'm new to ML. But I have an application that takes user input to generate paths/curves (All symbols are single paths) and I would then like to attempt ...
602 views

I've been researching on AdaBoost and GentleBoost classifiers, but can't seem to find a clear answer to the question: What is Adaboost better at classifying in computer vision? What is GentleBoost ...
2k views

### VC dimension of linear separator in 3D

I am confused about the Vapnik-Chervonenkis dimension of a linear separator in 3 dimensions. In three dimensions, a linear separator would be a plane, and the classification model would be "...
3k views

### Showing that Bayes classifier is optimal

Consider domain $X$, label set $Y=\{0,1\}$ and the zero-one loss. Given any probability distribution D over $X\times \{0,1\}$, we've defined the Bayes classifier $f_D$ to be-  f_{D}(x)= \...
1k views

### Training and testing image sizes for classification in computer vision

When training a classifier for object detection using features extracted from images (eg HoG features), how important is it that the images used for training fed into the classifier in their natural ...
55 views

### Simple Bayesian classification with Laplace smoothing question

I'm having a hard time getting my head around smoothing, so I've got a very simple question about Laplace/Add-one smoothing based on a toy problem I've been working with. The problem is a simple ...
523 views

### Decision Tree with Unbalanced Data

I have a data set with two classes: one class has at most 2000 members while the size of the second class is unlimited, though it is typically in the hundreds of thousands. I have read that it is ...
138 views

### What are the best features to identify heads from any angle?

I want to automatically track heads in CCTV records. Sometimes I need to re-identify heads because of multiple heads crossing each other. So I continually need to extract features from tracked heads ...
162 views

### some kernel and greater margin, how this occures?

I read following notes, and couldn't get it. any idea or hint would highly appreciated. a SVM classifier using a second order polynomial kernel. The first polynomial kernel maps each input data x to ...
741 views

### Why linear transformation can improve classification accuracy when the dimensionality of data is high?

Let $X$ be an $m\times n$ ($m$: number of records, and $n$: number of attributes) dataset. When the number of attributes $n$ is large and the dataset $X$ is noisy, classification gets more ...
3k views

### What would be a decent threshold for classification problem?

I'm using machine-learning algorithms to solve binary classification problem (i.e. classification can be 'good' or 'bad'). I'm using SVM based algorithms, ...
209 views

### What method of collective recogintion to use for digits recognition?

The structure of the question is as follows: at first, I provide the concept of collective recognition, further I provide explanation of the various methods of group classification that I found, in ...
247 views

### Language Classification + AWS ML: what am I doing wrong?

I'm evaluating Amazon's machine learning platform, and thought that I would give it a "simple" classification problem first. As a disclaimer, I am quite new to machine learning (hence my interest in ...
285 views

### machine learning classification with financial instrument/time series data

I am new to machine learning and have started brainstorming some model ideas that involve financial instrument/time series data. I was thinking it might be useful to use a classification algorithm to ...
75 views

### What is a visual bag of words and how is it implemented?

I'm currently working on implementing a bag of visual words in Python. I get the general gist of how it works but I can't seem to find any sources that explain it in more detail to a level where I can ...
60 views

### Classification algorithm for high dimensional data which is uniquely definable in a very small sub-space

I am new to machine learning, so forgive me if I am doing something absolutely absurd. I have a classification task (~100 classes) and have about 2 million training data points in a 2000-dimensional ...
102 views

### Environment requirement in training image dataset for classifier

I have a question about preparing the dataset of positive samples for a cascaded classifier that will be used for object detection. As positive samples, I have been given 3 sets of images: a set of ...
84 views

### Classification training data, but regression prediction

Suppose I'm performing machine learning on a simple dataset, and have a bunch of training data of the form: ...
927 views

### What is a sparse classifier?

Given a two-dimensional data set where each point is labeled $\{0,1\}$, I want to implement a sparse classifier with $L_p \ \text({ 0<p \leq 1) }$. I have been reading on logistic regression and ...
420 views

### What is the activation function, label and loss function for Hierachical Softmax

Several papers(1 (originator), 2, 3) suggest the use of Hierachical Softmax instead of softmax for classification where the number of classes is large (eg many thousand). I haven't been able to get ...
59 views

### Should Expectation Maximization take into account the Naive Bayes' independence assumption?

Should the independence assumption on which the Naive Bayes (NB) classifier is based, be taken into account when applying Expectation Maximization(EM) to infer missing values? The Naive Bayes ...
15k views

### Differences between SISD, SIMD and MIMD architecture (Flynn classification)

I have a problem with classifying certain CPUs to the proper classes of Flynn's Taxonomy. 1. Zilog Z80 According to this article on Sega Retro, Z80 has limited abilities to be classified as SIMD: ...
642 views

### Does programming language detection need more input than natural language detection?

I wonder which one of the two needs a larger input to achieve a decent accuracy: programming language detection or natural language detection? More details: Definition of Language detection: In ...
1k views

### Why is automatically labeling data in unsupervised learning hard?

I currently studying machine learning and pattern recognition area. Today, my professor said implementing an unsupervised system that automatically labels data is difficult. Why is that? I think if I ...
1k views

### kNN: how to improve Spam classification?

Currently I'm trying to classify spam emails with kNN classification. Dataset is represented in the bag-of-words notation and it contains approx. 10000 observations with approx. 900 features. Matlab ...
1k views

### Soft Margin Loss and Conditional Probabilities

Consider the following soft margin loss function: $\max(0, 1-yf(x))$. I have the problem of needing to compute the conditional probability $p(y|x)$ corresponding to this function and am having ...
626 views

### Environment detection - How to detect “city” versus “landscape” background environment in computer vision?

I'm searching for computer vision or machine learning algorithms/methods that are used to classify or differentiate two outdoor environments. Given an image with vehicles, I need to be able to detect ...
337 views

### How to tackle different sample size in the training set in SVM

I have to train a SVM for a classification problem. I have some strings that are the paths in a deterministic finite automata (DFA). If the alphabet is -01- then possible strings are 011101110 or ...
67 views

### What is the Best and easiest way to create a Classifer for Sentiment Analysis [closed]

Sentiment analysis using Machine Learning is a hot topic. In the present situation when a person doesn't have a problem in having the training data set then which way should we create the classifier ...
399 views

### What kind of Neural Network (if any) could fit two sets of data points?

I have two datasets, one of animal migration patterns (collected over the course of a couple years) that consists of many points on an x, y plane (latitude, longitude), and the other of ocean surface ...
50 views

### What values do $y_i$ in training data for binary classification problems attain?

In case of binary classification problem, what are the $y_i$ 's in the training data set $\{(x_1, y_1), (x_2, y_2), \dots (x_n, y_n)\}$? I guess they are from $\{1,-1\}$. Now I see a method for ...
49 views

### Finding Statistical Signifigance for a Classifier

I recently did work in the area of machine learning for one of my jobs and was able to build a classifier which evaluated to an F score of 85%. I also have access to correctly and incorrectly ...
1k views

### What kind of pattern recognition algorithm would Facebook use to detect suicidal users?

Facebook announced that it would employ a machine learning "reporting process using pattern recognition in posts previously reported for suicide" (https://newsroom.fb.com/news/2017/03/building-a-safer-...
66 views

### Classifying objects by set proximity

The project I'm working on has a number of objects arranged in overlapping sets. I need to classify them by whether they have a trait or not, using pre-classified objects that they are connected to (...
686 views

### Dynamically Learning Haar Cascade (in OpenCV)

I am new to computer vision so please excuse me if this question is very simple. I am trying to learn how to use the Haar Cascade creation tool provided with OpenCV to train a cascade classifier. It ...
76 views

### Classification when some classes are dependent

I think my problem can easier be explained via an example: Assume we have a dataset containing the images of 10 different mammals, let's say lion, elephant, cat, ... and horse. We have a 20-class ...
533 views

### Best algorithm for correlation between time series?

I have some biological data (ECG), which are quite chaotic in nature, and and some other data; that are not chaotic but related in some way, like fatigue. I want to find out how the time series, ...
42 views

### Subspace clustering with random transformation

One approach for clustering a high dimensional dataset is to use linear transformation, and the most common approaches are PCA and random projection (where random projection arises from the Johnson-...
24 views

### What is the purpose of standardization in machine learning?

I'm just getting started with learning about K-nearest neighbor and am having a hard time understanding why standardization is required. Reading through, I came across a section saying When ...
37 views

### k-means clustered data: how to label newly incoming data

I have a data set with labels that were produced by a $k$-means clustering algorithm. Now there is some data (with the same data structure) from another source and I wonder what is the most sensible ...
I have $8008$ binary grids of size $6 \times 10$ (they are all grids with the property described below), which I want to distinguish between with at most $13$ queries. A query will determine if the ...