Types of Matrices
Row Matrix
A matrix having only one row is called a row matrix or a row vector.
A = [aij]1×n
Column Matrix
A matrix having only one column is called a column matrix or a column vector.
A = [aij]m×1
Any matrix of order 1×1 can be treated as either a row matrix or a column matrix.
Square Matrix
A square matrix is a matrix in which the number of rows and the number of columns are equal. A matrix of order n×n is also known as a square matrix of order n.
A = [aij]n×n
The elements a11, a22, a33 … ann are called principal diagonal or leading diagonal or main diagonal elements.
The number of elements in a square matrix of order n is n2.
Diagonal Matrix
A square matrix A = [aij]n×n is said to be a diagonal matrix if aij = 0 when i ≠ j.
In a diagonal matrix, all the entries except the entries along the main diagonal are zero.
Triangular Matrix
A square matrix in which all the entries above the main diagonal are zero is called a lower triangular matrix. If all the entries below the main diagonal are zero, it is called an upper triangular matrix.
Scalar Matrix
A square matrix A = [aij]n×n is said to be scalar matrix if aij = a if i = j and aij = 0 if i ≠ j.
A scalar matrix is a diagonal matrix in which all the entries along the main diagonal are equal.
Identity Matrix or Unit Matrix
An identity matrix or a unit matrix is a scalar matrix in which entries along the main diagonal are equal to 1. the identity matrix of order n is represented as In.
Zero Matrix or Null Matrix or Void Matrix
A matrix is said to be a zero matrix or null matrix if all the entries are zero, and is denoted by O.