Feature (machine learning)

A feature (also characteristic ) is generally a recognizable characteristic that distinguishes a person, a thing or an abstract context of others.

The term " feature " that is occupied in the German language since the 17th century, based from the concept in the philosophy of the traditional doctrine, is the distinction between a being, of which the concept is predicable ( material object), and the content ( formal object ), which is included in this term (→ material object and formal object ). As connotation applies the feature or combination of features. The term is used both in the semantic meaning of symbols ( → Character; differentia specifica ) and in the sense of property.

Played a special role in classifying the feature of items in the taxonomy of the 17th century. In botany, it was Carl Linnaeus (1707-1778), who took the essential feature to the attention of its divisions to distinguish the different species of plants. According to him, the essential feature of " the most careful description of the development of the flower and fruit of the first kind was All other species of the genus are compared with the first, in which all non-uniform characteristics are excluded. After this work one obtains the essential feature ". Both Linnaeus and the botanist Joseph Pitton de Tournefort (1656-1798) defined the essential characteristic of a botanical genus. In this specific meaning of the term feature of Linnaeus and Tournefort was used in the sense of essence, nature and race.

For the philosopher Immanuel Kant (1724-1804) was a feature is "that makes things on a what of the same one in part of cognition ." The philosopher Georg Wilhelm Friedrich Hegel (1770-1831), however, wrote: "Nothing is so much even the Merkmahl the externality and the Verkommens of logic, as the popular category of Merkmahls. "

In biology in the mid- 20th century, the term " feature " in cladistics used with different meanings. On the one hand, the term " feature " in the meaning " structure of an organism " is used - and this meaning was connected to the idea that the "structure" obtained by changing to another state. On the other hand, the state in which a " structure " state, also referred to as a feature. Towards the end of the 20th century, the latter approach was usually preferred because it allows due to the distinction between ' feature' (English character) and character state ' (English character state) a more detailed description. Nevertheless, the attribute concept of some biologists was further defined in terms of " individual characteristics ".

The feature term is defined 9000:2005, Section 3.5.1 in DIN 55350 and DIN EN ISO.

Linguistics

In general linguistics features are properties of linguistic objects, see distinctive feature, feature structure, semantic feature.

Logic, theory of concepts

In modern logic, a distinction since Frege and often between the properties and the characteristics of a term.

Schriftvergleichung

In Schriftvergleichung characteristics are characteristics of graphical objects, such as Special features of the pressure system, the line quality, shape and motion control, motion flow, the direction of movement as well as the horizontal and vertical extent and surface structure.

Biology

Standard features for the description of a person such as age, height, hair and eye color.

These features affect all aspects of a living being, as they are examined in the subjects of morphology, ecology, physiology and behavior. Not all scientists even geographical distribution and abundance are considered as features.

The expression of a characteristic depends on both the genes and of external environmental influences. The genes lay in its entirety determines the tolerance range in which features can vary due to environmental influences. These environmentally controlled expression is referred to as a modification. Show individual species or groups of a special property, which did not appear at all other living beings, it is spoken by an exclusive feature (example: hair up to the skin occurs only in mammals on ).

Play a major role environmental influences, especially in ethology, when behavioral traits are formed only in the development of the individual by embossing or other forms of learning.

Only recently it is clear that mechanisms of self-organization play a role (examples: early embryonic network of nerve cells of the brain, formation of trabeculae ).

As part of the genetics we also speak of the phenotypic characteristics of living things.

The feature is considered by Jakob Johann von Uexküll as a control variable within the function circle.

Statistics and empiricism

In statistics, one speaks of a feature in terms of a raised value or a statistical variable.

Business management

In business, especially in sales and production, varied products due to their high number of different variants are described by a variety of characteristics. When the features are product characteristics that are typical for the product and clearly characterize the product from both customers as well as manufacturers view. The customer, the characteristics of its product can put together with the help of a product configurator itself. The features may either next to each other loose or be logically connected to each other and form an ideal Boolean Association. This makes it easier to achieve a consistent selection of product features.

Applied computer science

In applied computer science to use features of data in waveform ( images, voice ) in order to process the information better ( examples are the energy of a speech signal or an image, MFCC or LPC in speech recognition ). Various characteristics are often combined into feature vectors which facilitate pattern recognition.

Psychology

The term of the feature is used in the context of differential psychology and psychological assessment as Oberg term for all mental " attributes " of a person, in terms of the person can differ from others. One reason is that the concept of property in the strict sense ( trait English) for enduring personality characteristics is used, of which the states (german state) or behavioral habits (English habit ) can be distinguished.

Discrete and continuous variables

Discrete features

" Discreet are those features that only finitely many or countably can assume an infinite number of forms. In particular, all the features are discrete, their values ​​are determined by counting. " " Instead of discrete features one speaks also of discontinuous characteristics. "

Continuous features

"Continuous are those features that take on any real value, at least in a number interval and can therefore have uncountably many forms. [ ... ] Typical continuous variables are time, length, weight, volume, etc. "

Quasi Continuous Features

Discrete features that can accept an extremely high number of possible outcomes are sometimes referred to as quasi- steady. This is true for example in amounts of money that can be recorded to two decimal places. Of simplification and cost reasons, these " clearly discrete" partly by classification as at Einkommenensgrenzen. Conversely, they can also be at particular importance are " perpetuated ", which is for example the case if exchange rates to 5 decimal places are specified.

Quantitative and Qualitative Characteristics

• Quantitative characteristics are measured or counted. The characteristic values ​​are given as numeric values ​​plus unit. Possible values ​​are, for example, 30 cm for the term " length", and 5 kg for the term " weight ". Quantitative characteristics can be discrete or continuous variables.
• Qualitative characteristics are characteristics that can be described in words or numbers ( for example, 0 = red, 1 = green). " Qualitative characteristics are always discreet, because they inherently have only a countable set of possible feature values ​​( categories). "