## NEKG33 Mathematical methods for economists

## Chapter 22 : Day 22: Matrices

### By Lund University

Welcome to the matrix!

## Introduction to matrices

In the first section of this chapter we introduce matrices. We will then look at some special matrices such as diagonal matrices and the identity matrix. We then look at the row and column vectors and vectors in general.

#### Matrices, definitions

#### Special matrices

#### Row- and column vectors

#### Vectors

## Addition, scalar multiplication and transpose

We look at how to add to matrices and when you are allowed to add to matrices (same dimension). It is also possible to multiply and matrix by a scalar and we look at all the algebraic rules for matrix addition and scalar multiplication. In the final lecture we study the transpose of a matrix and related concepts such as symmetric matrices.

#### Matrix addition and scalar multiplication

#### Algebraic rules for matrix addition and scalar multiplication

#### Matrix transpose

## Matrices: Problems

Exercises on matrices