Matlab Tutorial 2: Matrices in Matlab

Matrices in Matlab

In the previous tutorial we have used the concept vector. This is a special case of matrix. A two-dimensional matrix is nothing but a rectangular table with its elements ordered in rows and columns. A matrix mxn consists of m rows and n columns. In Matlab this can be written for a matrix A.

A=
1 2 3
4 5 6

>> A= [ 1 2 3; 4 5 6 ] % semicolon separates rows.

This matrix A has 2 rows and 3 columns. The first row is: 1 2 3 and the second: 4 5 6 . For the columns we have the have following order: Column 1: 1,4 column 2: 2,5 and finally column 3: 3,6

Each entry in the matrix A is accessible by using the following indices:

A(row_index, column_index)

For instance try the following :

>> A(2,1)+A(2,3)+A(1,1) % adds three elements in A

or

>> A(1,1)=10 + A(2,2)

The most common matrix in matlab is the two-dimensional one. Many of the commands in matlab are only for valid for such matrices. The arithmetic operators (+, -, *, / and ^) that we used in tutorial1 can also be applied for matrices, but we also have some others as well.

Exercise 1: Vectors in Matlab

Generate a vector x=[5, -4, 6 ] with three elements. In Matlab as:

>> x=[ 5 -4 6]

or alternatively

>> x(1)=5; x(2)=-4; x(3)=6;

What is the answer of x(4) and x(0) ?

The indices in a vector starts from 1 and in this case ends with 3. Therefore to ask for x(4) and x(0) is pointless. Suppose we would have done differently creating the vector x. Read more »