From Wikipedia, the free encyclopedia Classification is a process related to categorization, the process in which ideas and objects are recognized, differentiated and understood. Classification is the grouping of related facts into classes.
Full Answer
Why are probabilistic classifiers useful?
Because of the probabilities which are generated, probabilistic classifier s can be more effectively incorporated into larger machine-learning tasks, in a way that partially or completely avoids the problem of error propagation.
What is the difference between binary and multiclass classification?
In binary classification, a better understood task, only two classes are involved, whereas multiclass classification involves assigning an object to one of several classes.
What are empirical tests?
Various empirical tests have been performed to compare classifier performance and to find the characteristics of data that determine classifier performance. Determining a suitable classifier for a given problem is however still more an art than a science.
How does a classifier work?
Other classifiers work by comparing observations to previous observations by means of a similarity or distance function. An algorithm that implements classification, especially in a concrete implementation, is known as a classifier. The term "classifier" sometimes also refers to the mathematical function, implemented by a classification algorithm, ...
What is Fisher's discriminant function?
Early work on statistical classification was undertaken by Fisher, in the context of two-group problems, leading to Fisher's linear discriminant function as the rule for assigning a group to a new observation. This early work assumed that data-values within each of the two groups had a multivariate normal distribution. The extension of this same context to more than two-groups has also been considered with a restriction imposed that the classification rule should be linear. Later work for the multivariate normal distribution allowed the classifier to be nonlinear: several classification rules can be derived based on different adjustments of the Mahalanobis distance, with a new observation being assigned to the group whose centre has the lowest adjusted distance from the observation.
What is a subclass of classification?
A common subclass of classification is probabilistic classification . Algorithms of this nature use statistical inference to find the best class for a given instance. Unlike other algorithms, which simply output a "best" class, probabilistic algorithms output a probability of the instance being a member of each of the possible classes. The best class is normally then selected as the one with the highest probability. However, such an algorithm has numerous advantages over non-probabilistic classifiers:
What is the performance of a classifier?
Classifier performance depends greatly on the characteristics of the data to be classified. There is no single classifier that works best on all given problems (a phenomenon that may be explained by the no-free-lunch theorem ). Various empirical tests have been performed to compare classifier performance and to find the characteristics of data that determine classifier performance. Determining a suitable classifier for a given problem is however still more an art than a science.
What is LCCN in the Library of Congress?
LCC should not be confused with LCCN, the system of Library of Congress Control Numbers assigned to all books (and authors), which also defines URLs of their online catalog entries, such as "42037605" and "https://lccn.loc.gov/42037605". The Classification is also distinct from Library of Congress Subject Headings, the system of labels such as "Boarding schools" and "Boarding schools—Fiction" that describe contents systematically. Finally, the classifications may be distinguished from the call numbers assigned to particular copies of books in the collection, such as "PZ7.J684 Wj 1982 FT MEADE Copy 1" where the classification is "PZ7.J684 Wj 1982".
Why was the LCC created?
It was designed specifically for the purposes and collection of the Library of Congress to replace the fixed location system developed by Thomas Jefferson. By the time Putnam departed from his post in 1939, all the classes except K (Law) and parts of B (Philosophy and Religion) were well developed. LCC has been criticized for lacking ...
What is LCC in library?
The Library of Congress Classification ( LCC) is a system of library classification developed by the Library of Congress in the United States , which can be used for shelving books in a library. It is used by most research and academic libraries in the U.S. and several other countries.
What letters are used in the National Library of Medicine?
The National Library of Medicine classification system (NLM) uses the initial letters W and QS – QZ , which are not used by LCC. Some libraries use NLM in conjunction with LCC, eschewing LCC's R for Medicine. Others use LCC's QP – QR schedules and include Medicine R.
What subclass is Java programming?
Java programming books in the QA subclass.
Does LCC cover authors?
^ LCCN also covers authors, which LCC does not. For authors (people), the letter 'n' accompanies the number, and they too define URLs in a parallel catalog, such as "n83160096" and "http://lccn.loc.gov/n83160096". (So LCCN may be called alphanumeric.)
Who invented the classification system?
The classification was invented by Herbert Putnam in 1897, just before he assumed the librarianship of Congress. With advice from Charles Ammi Cutter, it was influenced by his Cutter Expansive Classification, the Dewey Decimal System, and the Putnam Classification System (developed while Putnam was head librarian at the Minneapolis Public Library ).
Purpose
In the early 1900s, each branch of a United States government agency would conduct business analysis using its own methods and metrics, unknown and meaningless to other branches. In the 1930s, the government needed standardized and meaningful ways in which to measure, analyze and share data across its various agencies.
Structure
SIC codes have a hierarchical, top-down structure that begins with general characteristics and narrows down to the specifics. The first two digits of the code represent the major industry sector to which a business belongs. The third and fourth digits describe the sub-classification of the business group and specialization, respectively.
Uses
The U.S. Census Bureau, Bureau of Labor Statistics, Internal Revenue Service and Social Security Administration utilize SIC codes in their reporting, although SIC codes are also used in academic and business sectors. The Bureau of Labor Statistics updates the codes every three years and uses SIC to report on work force, wages and pricing issues.
Limitations
Over the years, the U.S. Census has identified three major limitations to using the SIC system. The first limitation surrounds its definition and mistaken classification of employee groups.
History of the change to NAICS
The Office of Management and Budget, or OMB, was tasked with revising the SIC system to reflect changing economic conditions. The OMB established the Economic Classification Policy Committee in 1992 to develop a new system representative of the current industrial climate.
Codes
The SIC codes can be grouped into progressively broader industry classifications: industry group, major group, and division. The first 3 digits of the SIC code indicate the industry group, and the first two digits indicate the major group. Each division encompasses a range of SIC codes:
Primeros Sistemas
- Época clásica y medieval
Los actuales sistemas de clasificación de las formas de vida descienden del pensamiento presentado por el filósofo griego Aristóteles, quién publicó en sus trabajos metafísicos y lógicos la primera clasificación conocida y que se cree es anterior a cualquier otra existente. Ésta es la … - Renacimiento
El profesor suizo Conrad von Gesner(1516-1565) hizo una aportación importante. El trabajo de Gesner fue una crítica compilación sobre las formas de vida conocidas hasta su época. La llegada al Nuevo Mundo produjo un gran número de nuevas plantas y animales aún no descrito…
Sistemas Modernos
- Características de los sistemas de clasificación
Independientemente de la escuela que la defina, el fin último de la taxonomía es presentar un sistema de clasificación que agrupe a toda la diversidad de organismos en unidades discretas dentro de un sistema estable, sobre las que les sea posible trabajar a los investigadores. Los sis… - Linneano
Dos años después de la muerte de John Ray, nació Carolus Linnaeus, conocido también como Carlos Linneo (1707–1778). Su gran trabajo, el Systema Naturae(primera ed. 1735), produjo 11 ediciones más durante su vida. En su trabajo, la naturaleza fue dividida en tres reinos: mineral, v…
Autoridades
- El nombre de cualquier taxón debe ser seguido de la "autoridad" (o autoridades) del nombre, esto es, el nombre del autor que por primera vez publicó una descripción válida de él. Estos nombres son frecuentemente abreviados: la abreviatura "L." Linnaeus, y en botánica existe una regulada lista de abreviaturas estándar (ver lista de botánicos por la abreviatura del autor). El sistema de …
Identificador Único Global
- Dentro de la comunidad de la Biodiversidad informática, existe una tendencia a ofrecer un Identificador único global en la forma de Identificador de las Ciencias de la Vida para todos los nombres biológicos. Este debería permitir autores de nombres de cita sin ambigüedades en medios electrónicos y reducir el volumen de errores en el deletreo de nombres o abreviaturas d…
Véase también
- Clasificación de los organismos en categorías altas (reinos, dominios, imperios)
- Nomenclatura binominal, Nomenclatura trinominal
- Cladística
- Clasificación filogenética
Referencias
- Esta obra contiene una traducción total derivada de «Biological classification» de Wikipedia en inglés, concretamente de esta versión, publicada por sus editores bajo la Licencia de documentación l...
Bibliografía
- Atran, S. (1990). Cognitive foundations of natural history: towards an anthropology of science. Cambridge, England: Cambridge University Press. xii+360 pages. ISBN 0521372933.
- Larson, J. L. (1971). Reason and experience. The representation of Natural Order in the work of Carl von Linne. Berkeley, California: University of California Press. VII+171 pages.
- Species 2000 & ITIS Catalogue of Life 2008
- Atran, S. (1990). Cognitive foundations of natural history: towards an anthropology of science. Cambridge, England: Cambridge University Press. xii+360 pages. ISBN 0521372933.
- Larson, J. L. (1971). Reason and experience. The representation of Natural Order in the work of Carl von Linne. Berkeley, California: University of California Press. VII+171 pages.
- Species 2000 & ITIS Catalogue of Life 2008
- Stafleau, F. A. (1971). Linnaeus and the Linnaeans. The spreading of their ideas in systematic botany, 1753–1789. Utrecht: Oosthoek. xvi+386 pages.
