1. BASIC MATLAB PROGRAMMING

2. Creating a vector or a matrix
As mentioned before, matrix (and vector) as the basic element of a Matlab program. Matlab does see mattix as other languages see numbers and can perform operations in matrix directly without a for loops.
Type :
>> x = [ ];
>> x
>> who
>> whos
>> y = [6; 7; 8; 9; 0; 9; 8; 7; 6]
(note that is there is a semicolon at the end of the instruction, matlab doesn't expand the result of the instruction)
>>y'
>> z = [1 2 3; 4 5 6; 7 8 9; 0 1 2]

3. Operators The colon operator:
A way to define quickly some vectors is to use the ":" operator. Type for instance (and observe the results):
Type :
>> a = 0:10
>> b = -5:10
>> c = 0:2:10
>> d = 10:-2:-5
>> e = 0:0.01:4.2
>> f = -pi:0.01:pi
You can see that these instructions are of the form lower limit: increment: upper limit

4. Operators
An other way to define elementary vectors that only contain ones and zeros: get help on zeros, ones, randn …
Try:
>> g = zeros(2,4)
>> h = ones(5,3)

5. Arithmetic Operators
These are the standard operators. (+ plus, - minus, / divide, * multiply, ^ exponent)
Try
>> 3^2
>> y'
>> x+y'
>> x*y
>> 3*x

6. Arithmetic Operators
The operators ( / , * and ^) have got a matrix counterpart (respectively ./ , .* and .^), which apply the operation element by element.
For instance, compare: x*y and x.*y.
Type:
>> x^2
>> x.^2
>> x.*x
>> x*x
if you type ">>whos" now, you will see that you have a lot of variables in the workspace. Type ">>clear", and ">>whos" again..

7. Matrix Operators Type A = [16 3 2 13; 5 10 11 8; 9 6 7 12; 4 15 14 1]
sum(A) % displays the sum of the columns of A.
>>sum(A)
>>
sum(sum(A)) % dsiplays the sum of A
A’ % Transpose conjugate (if complex number) else transpose.
>> A’
>>sum(A’) % Sum of the lines of A (columns of A’). Note that functions can be
% combined very easily.

8. Matrix Operators
Try A(4,2)?
Try A(4,5)?

9. For Loops Do, ima = zeros(100,100); for i = 1:100 for j = 1:100
ima(i,j) = i+j;
end
WHAT HAPPENS?

10. Plotting with Matlab/Graphics
Matlab contains many powerful functions for easily creating plots of several different types. Try this one:
>> x=[0:0.001:10];
>> y=sin(2*x);
>> figure(1);plot(x,y);xlabel(‘paksi-x’),ylabel(‘paksi-y’);
>> title(‘plot y=sin 2x’);

11. Matlab Scripting files & the Editor/Debugger
You can perform operations in Matlab in 2 ways:
Using Matlab Command Window
Using Editor/Debugger (.m file)
Example of Scripting file:
% coordinate_polar
% program ini untuk menukar koordinat (x,y) kepada koordinat polar.
x = input ('Enter the value of x: ');
y = input ('Enter the value of y: ');
r = sqrt(x^2+y^2);
if x>=0
theta = atan(y/x);
else
theta = atan(y/x)+pi;
end
disp('The hypoteneus is: ')
disp(r)
theta = theta*(180/pi);
disp('the angle in degree is: ')
disp(theta)
Example of Matlab Function File:
% program ini adalah untuk mengira luas bulatan.
% A = 4 pi r^2.
function [A]=luas_bulatan(r)
A=4*pi*r^2;
fprintf('luas bulatan adalah %f', A);

12. Example:
Write a script file using conditional statements to evaluate the following function, assuming that the scalar variable x has a value. The function is for x  0, for 0  x  10, and for x  10.
Use for loop to plot the above function over the interval -2  x  12. Properly label the plot. The variable y represents amplitude in volts, and the variable x represents frequency in hertz. Give title for the graph as ‘Amplitude versus frequency’.
Answer:
x=[-2:0.01:12];
for n=1:length(x)
if x(n)<0
y(n)=sqrt(x(n)^2+1);
elseif x(n)>=10
y(n)=9*sin(5*x(n)-50)+31;
else
y(n)=3*x(n)+1;
end
plot(x,y);grid;
xlabel('frequency(hertz)');
ylabel('amplitude(voltz)');
title('amplitude versus frequency');

13. Plot of the amplitude versus frequency