# What is Classification: Definition and 114 Discussions

Classification is a process related to categorization, the process in which ideas and objects are recognized, differentiated and understood. See Classification (general theory)
It may also refer to:

View More On Wikipedia.org
1. ### I How do leaf nodes behave in regression decision trees?

Hello. Decision trees are really cool. They can be used for either regression or classification. They are built with nodes and each node represents an if-then statement that gets evaluated to be either true or false. Does that mean there are always and only two edges/branches coming out of an...

3. F

### Stationary points classification using definiteness of the Lagrangian

Hello, I am using the Lagrange multipliers method to find the extremums of ##f(x,y)## subjected to the constraint ##g(x,y)##, an ellipse. So far, I have successfully identified several triplets ##(x^∗,y^∗,λ^∗)## such that each triplet is a stationary point for the Lagrangian: ##\nabla...
4. ### Classification of a second order partial differential equation

Hello! Consider this partial differential equation $$zu_{xx}+x^2u_{yy}+zu_{zz}+2(y-z)u_{xz}+y^3u_x-sin(xyz)u=0$$ Now I've got the solution and I have a few questions regarding how we get there. Now we've always done it like this.We built the matrix and then find the eigenvalues. And here is...
5. ### Why it doesn't sum to one in this simple naive Bayes classification?

Summary:: When we have only three classes (Orange, Banana and Other) and three features (Long, Sweet and Yellow), why P(Other|Long, Sweet, Yellow) + P(Banana|Long, Sweet, Yellow) is not equal to 1 when P(Orange|Long, Sweet, Yellow) = 0 ? In this example...
6. T

### Classification of mathematical objects

Hello. When does someone know a classification of some kind of mathematical objects has been completed? For example of differentiable manifolds, or abelian groups or ordered fields? Thank you.
7. ### Clustering and Classification in Machine Learning

Hello, I started studying machine learning and its basics. One of the applications of supervised learning ML is classification, i.e. identifying different objects and classify them. Being supervised means that the ML algorithm is initially served labelled data. The labelled data is used to a)...
8. ### Library classification of mathematical fiction

Imagine that you are a librarian or a book-seller, and you come across a book which is a cross between mathematical fiction and mathematics popularization: that is, it is heavier on the mathematics explanations than a work of fiction has a right to be, yet it is heavier on plot, much of which...
9. ### How are ancestors classified in a cladistic system?

Hi all, When I first learned about cladistics, it seemed like an elegant and objective way of classifying life - forget about subjective physical similarities, classify purely based on scientifically testable ancestry, and have all taxa be monophyletic clades, so everything in one taxon is more...
10. ### Signal classification and processing for a gesture sensor module

I got a gesture sensor module that produces a signal per event. The each signal is a set of regularly sampled readings from four photodiodes. The number of samples per event can be very different, from around 20 up to over 100, and each sample value is essentially the measured brightness...
11. ### [Neural Networks] Classification of a sick brain

Hi, i have a dataset with MRI of patients with a specific disease that affects the brain and another dataset with MRI of healthy patients. I want to create a classifier (using neural networks) to classify if the MRI of a new patient show the presence of the ill or not. First of all, i...
12. ### I Spectrum classification and dimension reduction

I am trying to distinguish two different plant species based on their chemical signature using statistical signal classification. This is what the average curves of two species look like with their standard deviation bounds: These spectra are made up of ~1400 points. So it was suggested to...
13. ### I What number classification does i*e, or i*sqrt(2) belong to?

I have been told that irrational and transcendental numbers only belong to the set of real numbers. But what if you multiply one by i? Is it now an “imaginary irrational” or “imaginary transcendental” number?Based on a quick google while making this thread, Wikipedia says that transcendentals...
14. ### I Classification of First Order Linear Partial Differential Eq

How can I classify a given first order partial differential equations? Are all first order linear PDEs hyperbolic? Quora Link:https://www.quora.com/How-do-I-classify-first-order-PDE-elliptic-hyperbolic-or-parabolic-using-method-of-characteristics
15. ### Python Shuffling in classification problems

Hello all, This is not particular to Python, it is more conceptual related to machine learning algorithms, specifically the nearest neighbor classifiers. So, I have this dataset with m examples, each with n features and one target feature. The dataset is originally ordered such that similar...
16. J

### I Is my classification of transcendental correct?

From what I've recently read, Transcendental numbers are those irrational numbers which cannot be formed by sqrt or any root of any order. So If the irrational numbers which are formed by taking roots of different orders on numbers which are not perfect roots of that order, it is called as a...
17. ### Is oil shale considered a biochemical sedimentary rock?

Could we classify oil shale as a biochemical sedimentary rock ? Oil shale is a muddy rock contains Kerogen. So I think in oil shale to be a mixture of Kerogen and mud sediments, and that's not the case, for instance, with the biochemical limestone where the solid remains of the living organisms...
18. ### Different classification of subfields of Physics.

Dear members, I'm having trouble distinguishing between classical and modern physics subfields and theoretical and experimental classification when compared to the classification listed: 1, Nuclear and particle physics 2. Atomic, molecular, and optical physics 3. Condensed matter physics 4...
19. ### A Spectral Classification Syntax for Binaries

for α Cnc one gets from http://simbad.u-strasbg.fr/simbad/sim-id?Ident=alpha+cancri a spectral type of kA7VmF0/2III/IVSr I don't get behind this special use of "/" - Syntax - what's that that meant to denote? kA7Vm+F02III xor kA7Vm+F02IVSr? Anything else?
20. ### I Classification of differential equation

Hi, I have an equation that takes the form: ax''-by' + c = 0 where x'' is second order with respect to time and y' is first order with respect to time. Would this be classed as a partial differential equation? Thanks very much for your help :)
21. ### Flynn's Taxonomy as a modern classification

Flynn's Taxonomy was a classification of computer architectures published in 1966. Computing has changed a lot since then. Is this taxonomy still useful? What are some of its shortcomings for evaluating modern computing systems?
22. ### I Objective classification of spiral galaxies

I have question that has been troubling me and I was hoping someone may be able to help me. I've always thought the Hubble classification of galaxies was a bit subjective. I was recently looking at some images online of galaxies and I was wondering how you might objectively observe and compare...
23. ### A Optimization problem classification

Here all, Here's a problem I'm trying to solve. Given a planar piecewise linear and circular curve (ie. a curve consisting of line and circular arc segments) that represents the path of a particle; a set of rules for traversing the two types of curve segments as well as the transitions between...
24. ### What Are the Taxonomic Classifications of Algae?

Does algae fall under the plant kingdom or thr protista kingdom? Why does blue-green algae fall under thr kingdom monera if it is a kind of algae? Thanks for any help in advance!
25. ### EQualityCoin- What type of model is this?

Hi everyone, I've been working on developing a crypto-currency called eQualityCoin for a while now and hoped someone here might be able to help me "classify" the system in a formal mathematical sense. The system's main feature is a simple rule for how it determines a purchaser's exchange...
26. ### I Simple machine classification (can o worms?)

Hello all. I have a question concerning the classification of simple machines, of which classically there are considered to be 6. I have joined the camp which claims there are only 2 true simple machine categories at the most fundamental level. The lever and the inclined plane. I will be happy...
27. ### I Is it better to use a regression or a classification?

Hi everyone, I am looking at an interesting problem at work, and I would like to hear your opinion about it, please. I'll try to explain it as concisely as I can. We took about 2500 chemical compounds and we tested them in some 'phenotypic assays'. The assays give as output an activity value...
28. ### I Clarification of classification of ODE

Hi there dr/dz+z^2=0 is classified as a non-homogeneous in Glyn James text, can someone clarify this? Cheers Petra d.
29. ### B Planet/Dwarf Planet Classification - Regarding Rogue Bodies

Hi there, I was reading up on how planets are classified based on their size, but ran into a problem when I began to consider rogue celestial bodies. If a body has significant enough mass to maintain a hydrostatic equilibrium, yet doesn't orbit a star, I understand that it's classified as a...
30. ### Importance of classification in eukaryotes

Eukaryotes are classified into unicellular and multicellular,what makes this classification so important?
31. ### Classification of multipartite entanglement

Good Morning. I need some help according to how to classify the multipartite state. from my reading, the classification according to Local Unitary (LU) and stochastic local operation and classical communication (SLOCC). How the state can be classify from LU to SLOCC?
32. ### Fission neutron classification

"Looking at time behaviour of neutrons in a reactor on time scales of both ~sec and ~days/months Start with fission process e.g. 235U + n -> 236U ->fission Usually divide into 2 Fission Fragments 10%-20% of fission emit a scission neutron (i.e. at time of scission)" I've heard...
33. ### Engineering How important is classification of degree (engineers)?

I'm asking this mainly to engineers but anyone can answer. How important is the classification of degree that you receive and what has it's impact been on your career? I plan to work in industry and eventually towards chartered/professional status then management positions. For my MEng...
34. ### Classification of the equation

Homework Statement Here is the equation: Homework Equations What kind of equation is it(homogenous linear, unhomogenous linear, quazilinear...) The Attempt at a Solution I suppose it is a homogenous linear one...
35. ### What Are the Periodic Trends and Properties of Atomic Elements?

I need a link or questions on periodic trends or periodic properties like on atomic radius,ionic radius,ionization energy,electron affinity,electropositivity and electonegativity Thanks Nusaiba mustafa
36. ### Binary classification: error probability minimization

Typically in problems involving binary classification (i.e. radar detection, medical testing), one will try to find a binary classification scheme that minimizes the total probability of error. For example, consider a radar detection system where a signal is corrupted with noise, so that if the...
37. ### Question on possible dark matter classification

Hello It is my understanding that the matter originally contained in a dying star which formed a black hole has been entirely converted to energy in the form of space time curvature. In other words the matter no longer exists and all that is left is the curvature of spacetime. Aside from my...
38. ### Stargazing Quick question about telescope classification

I am slightly confused about what the term 'astronomical telescope' covers. My textbook seems to be implying that astronomical telescopes are refracting telescopes with an objective and eyepiece lens, and reflecting telescopes are separate to astronomical telescopes. On the other hand I have...
39. ### "Robustness" of Nielsen-Thurston Classification

Hi all, Let X be a nice-enough topological space so that it admits a universal cover ## \tilde X ## When does a homeomorphism ## h: X \rightarrow X ## give rise to a homeomorphism of the universal cover to itself, i.e., we have ## p: \tilde X \rightarrow X ## , then, by lifting...
40. ### Classification of conformal anomalies

I know what a Weyl anomaly is. I see terms like "type-A" anomaly and "D-type" anomalies in the literature. What does this classification refer to, and where was it originally introduced? Specifically, what does a D-type Weyl anomaly mean?
41. ### Stellar Classification Limits: Temperature & Magnitude

Is there a specific limit that defines the boundaries of each classification category? For example, a main sequence G class star is between X and Y temperatures and has an absolute magnitude between A and B Solar units. Or, an O hypergiant is between X and Y temperatures and has an...
42. ### MHB Using Classification of Poles to Calculate Residues

Hi guys i wanted to clear out some confusion, Suppose $\text{z=a}$ is a simple pole, my Professor classify it as follows: Simple Pole at z=a Type 1: $$f(z)=(z-a)^{-1}g(z),g\in H(D(a;r)):$$ $$Res\{f(z);a\}=g(a)$$ Type 2: $$f(z)=\frac{h(z)}{k(z)},h(a)\neq 0,k(a)=0,k^{'}(a)\neq 0:$$...
43. ### Classification of Second-Order PDE with Constant Coefficients

Homework Statement I have 3 equations: \frac{\partial^2 u}{\partial t^2}+\frac{\partial^2 u}{\partial x \partial t}+\frac{\partial^2 u}{\partial x^2} \frac{\partial^2 u}{\partial t^2}+4\frac{\partial^2 u}{\partial x \partial t}+4\frac{\partial^2 u}{\partial x^2} \frac{\partial^2...
44. ### Classification of Elastic and Inelastic scattering

Hi, I am slightly confused regarding the termenology elastic and inelastic. My focus is on the interactions, Rayleigh, photoelectric, comptonscattering and pair production. I have read around the internet and have some question I did not fully got answered. 1) Is Elastic = Coherent and...
45. ### Is There a Universal Classification System for All Things?

Is there a classification of all things? This question actually arises from the 20 Q game. If things are categorized and arranged as a tree, it would be very easy. I don't think there exist such a categorization (who has the time!) but still is it possible? You could start with natural and...
46. ### Interspecies mating and animal classification

I just read about how coyotes and dogs can interbreed, and their offspring can also breed. I thought one of the classifications of species was that two different species could either not breed together, or their offspring would be infertile. Dogs are of the species canis lupus, and coyotes are...
47. ### Classification of Gravitational Theories

hi there are many gravitational theories such as 1- modified gravity { massive gravity, dilaton gravity, ... } 2-conformal gravity 3-emergent gravity 4-lower and highest dimensional gravity 5-... is anybody know about this gravitational theories? is there a general classification of...
48. ### Classification of manifolds and smoothness structures

Except for the work of Torsten I am not aware of any paper which discusses these topics. Some ideas: 1) all theories for QG I am aware of do either use manifolds and smootheness (string theory, geometrodynamics, shape dynamics, ...) or are constructed from them (LQG, CDT, ...) 2) in some...
49. ### Problem understanding Wigner's classification

Wigner classified particles in function of the eigenvalues of P_\mu P^\mu and W_\mu W^\mu. Then, it can be proved that for massless particles spin values can be only \pm s_{max}. But for a particle with mass could have intermediate spin values. 1. If we think that a massless particle is the...
50. ### Is a Semidirect Product Involving Z_7, Z_3, and Z_2 Isomorphic to Z_7 and Z_6?

Checking to see whether semidirect products are isomorphic. Homework Statement I want to simplify this semidrect product (Z_7 \rtimes_{\bar{\alpha}} Z_3) \rtimes_{\alpha} Z_2, but I'm not sure how. In other words, I want to see if this is isomorphic to (for example) Z_7 \rtimes_{\alpha}...