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In mathematics, a generalized inverse of a matrix ''A'' is a matrix that has some properties of the inverse matrix of ''A'' but not necessarily all of them. Formally, given a matrix and a matrix , is a generalized inverse of if it satisfies the condition . The purpose of constructing a generalized inverse is to obtain a matrix that can serve as the inverse in some sense for a wider class of matrices than invertible ones. A generalized inverse exists for an arbitrary matrix, and when a matrix has an inverse, then this inverse is its unique generalized inverse. Some generalized inverses can be defined in any mathematical structure that involves associative multiplication, that is, in a semigroup. == Types of generalized inverses == The Penrose conditions are used to define different generalized inverses: for and AA^= A^ |- | 3.) || |- | 4.) || . |} If satisfies condition (1.), it is a generalized inverse of , if it satisfies conditions (1.) and (2.) then it is a generalized reflexive inverse of , and if it satisfies all 4 conditions, then it is a Moore–Penrose pseudoinverse of . Other various kinds of generalized inverses include * One-sided inverse (left inverse or right inverse) If the matrix ''A'' has dimensions and is full rank then use the left inverse if and the right inverse if * * Left inverse is given by , i.e. where is the identity matrix. * * Right inverse is given by , i.e. where is the identity matrix. * Drazin inverse * Bott–Duffin inverse * Moore–Penrose pseudoinverse 抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)』 ■ウィキペディアで「Generalized inverse」の詳細全文を読む スポンサード リンク
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