Definitions

• Matrix
  • A 2-dimensional array of real numbers
  • An m by n matrix has m rows and n columns

    

    -- element at ith row and jth column.

• Vector
  • A 1-dimensional array of real numbers
  • A row vector (of size n) -- a matrix with 1 row

    

  • A column vector (of size m) -- a matrix with 1 column

    

  • By default, a vector is a column vector
• Some special matrices
  • Identity matrix,

    

  • Diagonal matrix,

    

  • Tridiagonal matrices,

    

  • Lower-triangular matrices,

    

  • Upper-triangular matrices,