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This introduction covers matrix definitions, properties, and basic operations including addition, multiplication, powers, transposes, and Boolean matrices. It explains key concepts with examples and outlines the properties of square matrices. Learn about symmetric and Zero-One matrices.
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A very brief introduction to Matrix (Section 2.7) • Definitions • Some properties • Basic matrix operations • Zero-One (Boolean) matrices
row column Matrix (Section 2.7) Definition:A matrix is a rectangular array of numbers. A matrix of m rows and n columns is called an mn matrix, denoted Amn. The element or entry at the ith row and jth column is denoted ai,j. The matrix can also be denoted A = [ai,j]. Example a2,3 = 2
Matrix Two matrices Amn and Bpq are equal if they have the same number of rows and columns (m = p and n = q), and their corresponding entries are equal (ai,j =bi,j for all i, j). Amn is a square matrix if m = n, denoted Am A square matrix A is said to be symmetric if ai,j = aj,ifor all i and j.
Matrix arithmetic (operations) Matrix addition. Amn and Bmn • must have the same numbers of rows and columns • add corresponding entries Amn + Bmn = Cmn = [ai,j + bi,j] Matrix subtraction is done similarly
Matrix arithmetic (operations) Multiply a matrix by a number. • bA = [bai,j] (i.e., multiply the number to each entry.) Multiplication of two matrices. Amk and Bkn • number of columns of the first must equal number of rows of the second • the product is a matrix, denoted AB = Cmn • Entry ci,j is the sum of pair-wise products of the ith row of A and jth column of B
Matrix arithmetic (operations) Example
Powers of (square) matrixAn A0 = In =, Ar = AA···A r times Powers and Transposes Identity matrix: In • A square matrix of n rows and n columns • Diagonal entries are 1, all other entries are 0 (ii,i= 1 for all i, ii,j= 0 for all i != j.) • For matrix Amn, we have Im A = A In = A
Powers and Transposes Matrix transpose: Amn • the transpose of A, denoted At, is a n m matrix • At = [bi,j = aj,i] • ith row of A becomes ith column of At Theorem: A square matrixAnis symmetric iff A = At
Zero-One (Boolean) Matrix Definition: • Entries are Boolean values (0 and 1) • Operations are also Boolean • Matrix join. • A B = [ai,j bi,j] • Matrix meet. • A B = [ai,j bi,j] Example:
Zero-One (Boolean) Matrix • Matrix multiplication: Amk and Bkn • the product is a Zero-One matrix, denoted AB = Cmn • cij = (ai1 b1j) (ai2 b2i) … (aik bkj). • Example: