affine transformation

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affine transformation

[ə′fīn ‚tranz·fər′mā·shən]
(mathematics)
A function on a linear space to itself, which is the sum of a linear transformation and a fixed vector.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Affine Transformation

a pointwise mutually single-valued mapping of a plane (space) onto itself in which straight lines are transformed into straight lines. If a Cartesian coordinate system is given in a plane, then any affine transformation of this plane can be defined by means of a so-called nonsingu-lar linear transformation of the coordinates x and y of the points of this plane. Such a transformation is given by the formulas x’ = ax + by + p and y’ = cx + dy + q with the additional requirement that . Analogously, any affine transformation of a space can be defined by means of nonsingular linear transformations of the coordinates of points in space. The set of all affine transformations of a plane (space) into itself forms a group of affine transformations. This denotes, in particular, that the successive execution of two affine transformations is equivalent to some single affine transformation.

Examples of affine transformations are the orthogonal transformation—a motion of a plane or space or motion with a reflection; the transformation of similitude; and uniform “compression.” A uniform “compression” with coefficient k of the plane π toward a straight line a located in it is a transformation in which the points of a remain stationary and every point M of the plane π which does not lie on a is displayed along a ray passing through M perpendicularly to a to a point M’ such that the ratio of the distances from M and M’ to a is equal to k. Analogously, one defines a uniform “compression” of space to a plane. Each affine transformation of the plane can be obtained by performing a certain orthogonal transformation and a successive “compression” on some two perpendicular lines. Any affine transformation of space can be accomplished by means of a certain orthogonal transformation and successive “compressions” on some three mutually perpendicular lines. In an affine transformation, parallel lines and planes are transformed into parallel lines and planes. The properties of the affine transformation are widely used in various branches of mathematics, mechanics, and theoretical physics. Thus, in geometry the affine transformation is used for the so-called affine classification of figures. In mechanics, it is used in the study of small deformations of continuous media; in such deformations, small elements of the medium in the first approximation undergo affine transformations.

REFERENCES

Muskhelishvili, N. I. Kurs analiticheskoi geometrii, 4th ed. Moscow, 1967.
Aleksandrov, P. S. Lektsii po analiticheskoi geometrii. Moscow, 1968.
Efimov, N. V. Vysshaia geometriia, 4th ed. Moscow, 1961.
E. G. POZNIAK

affine transformation

(mathematics)
A linear transformation followed by a translation. Given a matrix M and a vector v,

A(x) = Mx + v

is a typical affine transformation.
References in periodicals archive ?
where [u.sup.*.sub.i] (k | k) and [x.sup.*.sub.i] (k | k) denote the piecewise affine function of [u.sup.*] (k | k) and [x.sup.*](k | k) with respect to x(k) in partition [P.sub.i], respectively.
BEHAVIOR OF T-LINEAR AFFINE FUNCTIONS AT THE BOUNDARY
In MMALPHA, a COB can be applied to any local variable, say X, using any affine function, T that admits a left inverse [T.sup.-l] for all points in the domain of X.
In the case where the function h is an affine function, the even contest occurs when [Alpha][Sigma] = 1.
For example, f ([x.sub.1], [x.sub.2]) = [x.sub.1] [direct sum] [x.sub.2] is an affine function, while the function, f ([x.sub.1], [x.sub.2]) = [x.sub.1] [direct sum] [x.sub.2] [direct sum] [x.sub.1] x [x.sub.2] is not an affine function, where,.
Specifically, the profit functions of the supply chain members are no longer affine functions of the supply chain system's profit function.
Specifically the profit functions of the supply chain members are no longer affine functions of the supply chain system's profit function.
This applies for example to piecewise affine functions. It is also noteworthy that a sum of two risk vulnerable functions need not be risk vulnerable.
They cover cones, cones in topological vector spaces, Yudin and pull-back cones, Krein operators, K-lattices, order extensions, piecewise affine functions and in a fascinating appendix, linear topologies.
When K is a compact convex set, we will denote the order unit space of continuous real-valued affine functions on K by Aff (K).
From (11), it can be seen that the profit functions of the supply chain members are all affine functions of the whole supply chain's profit function.

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