MATLAB TUTORIAL 3- WORKING WITH MATRIX PART 1

Hii friends I am here with another MATLAB tutorial, this time we are going to discuss about matrix operations in MATLAB, MATLAB  supports  two types of operations,  known as matrix  operations  and array operations.  Matrix operations  will be discussed first.

Matrix generation

 Matrices are fundamental  to MATLAB. Therefore,  we need to become familiar with matrix generation  and manipulation. Matrices can be generated  in several ways.

  Entering  a vector

 A vector is a special case of a matrix.  The purpose of this section is to show how to create vectors and matrices in MATLAB.The elements of vectors in MATLAB are enclosed by square brackets  and  are separated  by spaces or by commas. For example, to enter a row vector, v, type

>> v = [1 4 7 10 13]

v   =

1      4      7      10      13

Column  vectors  are  created  in a similar  way,  however,  semicolon (;)  must  separate  the components  of a column vector,

>> w = [1;4;7;10;13]

w   =

1

4

7

10

13

 On the other hand, a row vector is converted to a column vector using the transpose operator. The transpose  operation  is denoted  by an apostrophe  or a single quote (’)               

    >> w = v’

w   =

1

4

7

10

13

Thus, v(1) is the first element of vector v, v(2) its second element, and so forth. Furthermore, to access blocks of elements, we use MATLAB’s colon notation  (:).  For exam-

ple, to access the first three  elements of v, we write,

>> v(1:3)

ans =

1     4     7

 Or, all elements from the third  through  the last elements,

>> v(3,end)

ans =

7     10     13

 where end signifies the last element in the vector.  If v is a vector, writing

>> v(:)

 produces a column vector, whereas writing

>> v(1:end)

produces a row vector.

Entering  a matrix

 A matrix  is an array of numbers.  To type a matrix  into MATLAB you must

• begin with a square bracket,  [,• separate  elements in a row with spaces or commas (,)

• use a semicolon (;) to separate  rows,• end the matrix  with another  square bracket,  ].

Here is a typical example.  To enter a matrix  A, such as,

   1   2   3

A =    4   5   6

            7  8   9

>> A = [1 2 3; 4 5 6; 7 8 9]

MATLAB then  displays the 3 × 3 matrix  as follows,

A    =

1	2	3
4	5	6
7	8	9

Note that  the  use of semicolons (;)  here is different  from their  use mentioned  earlier  to

suppress output or to write multiple  commands in a single line.

Once we have entered  the matrix,  it is automatically stored  and remembered  in the

Workspace.  We can refer to it simply as matrix  A. We can then view a particular element in

a matrix  by specifying its location.  We write,

>> A(2,1)

ans   =

4

 A(2,1) is an element located in the second row and first column.  Its value is 4.

Matrix indexing

We select elements  in a matrix  just  as we did for vectors,  but  now we need two  indices. The

element  of  row  i and column j of the matrix  A is denoted  by A(i,j).  Thus,  A(i,j) in MATLAB refers to the  element Aij  of matrix  A. The  first  index is the  row number  and the second index is the column number.  For example, A(1,3) is an element of first row and third column.  Here, A(1,3)=3.

Correcting  any  entry  is  easy  through  indexing.     Here  we substitute A(3,3)=9 by

A(3,3)=0.  The result  is

>> A(3,3) = 0

A	=
	1	2	3
	4	5	6
	7	8	0

Single elements of a matrix  are accessed as A(i,j), where i ≥ 1 and j ≥ 1. Zero or negative

subscripts are not supported  in MATLAB.

Their are many more thing left so continue to  MATLAB TUTORIAL 3- WORKING WITH MATRIX PART 2