1. Introduction To Matlab Class 1
Instructors: Hristiyan (Chris) Kourtev
and Xiaotao Su, PhD
Double click the matlab icon
When prompted click “Skip”, then type:
mkdir C:/MatlabClass/YourLastName
cd C:/MatlabClass/YourLastName

2. http://ruccs.rutgers.edu/matlab_course/ Introduction Ask Questions!
Slides, notes, assignments, and other info will be at:

3. Setup Click Matlab mkdir C:/MatlabClass/YourLastName
cd C:/MatlabClass/YourLastName

4. Programming Matlab has its own programming language What is a program?
A series of instructions that the computer follows
Also referred to as “Code” or a “Script”

5. Two Options For Where To Issue Commands/Instructions
In the command window
In a script (program) executed by the command window.

6. Note: The “_” character is the shifted dash SHIFT + -
Hello World
At the command prompt type: my_var = ‘hello world’; And press ENTER.
Note: The “_” character is the shifted dash SHIFT + -

7. Hello World my_var = ‘hello world’;
Semi-colon is so you don’t output the result to the screen.
Single quotes denote character string
Variable Name

8. Variables num_oranges = 3.5 num_apples = 7 7 3.5 my_var num_oranges
my_var = ‘hello world’;
num_oranges = 3.5
num_apples = 7 7
‘hello world’
3.5
my_var
num_oranges
num_apples
Variable Name

9. Memory Your computer’s memory
Each of the values are stored in memory associated with the variable name
The “who” command will list the current variables in memory
Typing my_var will return the value of that variable
Var Name
Value
my_var
‘hello world’
num_apples 7
num_oranges
3.5
subject_name
‘john smith’ …

10. Setting values
As you have seen you set the value of a variable with the “=“ sign
You can also set a variable equal to another variable or the output of an operation on a variable.

11. Setting values new_var = my_var third_character = my_var(3) this is 7
fruit = num_apples + num_oranges
this is now 10.5
num_apples = 6
what is the value of fruit now?

12. Changing around strings
my_var is currently ‘hello world’
Typing my_var(3) will return ‘l’ my_var(3) = my_var(1) Now what is the value of my_var?

13. Calling Functions
A function is a program that you call on to do some sort of action
length(‘hello world’)
length(my_var)
disp(my_var)

14. disp( length(‘hello world’) )
Nesting Functions
disp(length(my_var))
What happens here?
disp( length(‘hello world’) )
disp(11) 11

15. Your first program What is pseudo-code and why we need it
Typing commands one at a time isn’t very efficient, especially when you want to do the same ones repeatedly…
so we create a program to do it
This program will be called mix_strings

16. Comments Comments are descriptions of what is happening in your code.
They are need to follow what is happening for debugging purposes
At the beginning of a script you put in a type of comment called a header

17. % symbol makes this line “commented out” This means that the computer will ignore these lines
These lines aren’t for the computer, they are for you
% mix_strings.m % % Displays the string ‘hello world’ % Then scrambles letters in that string and % displays the scrambled string % written by XYZ 3/6/2005
Name of file
Description: What does this file do?
Who wrote it and when?

18. So what is the header good for?
Save the file
At the command line type:
help mix_strings
All matlab programs have headers. Find out information on disp, pause, and length

19. What else?
lookfor can be used to search for programs that have certain words in their headers.
lookfor string
lookfor random

20. Back to the program
clear all; my_var = ‘hello world’; mixstr = my_var; mixstr(3) = my_var(1); mixstr(1) = my_var(3); disp(mixstr);

21. Now run it
In the command window:
mix_strings

22. loops for i=1:5 disp(i) end;
Used to repeat the same chunk of code many times
for i=1:5
disp(i)
end;

23. mix_strings2.m
clear all; my_var = ‘hello world’; mixstr = ‘xxxxxxxxxx’; for i=1:length(my_var) mixstr(i) = my_var(i); end; disp(mixstr)

24. rand and ceil rand will create a random number from 0 to 1
ceil will round up any number to the next integer
Together you can create random integers ceil(rand*7)

25. task 1
Replace each x in mixstr with a random character from my_var. Start with the first x, then the second x… ‘hello world’ ‘xxxxxxxxxxxxx’ Result could be -> ‘wdolhrdlhlwe’

26. % mix_strings3.m %
%Displays the string 'hello world‘, then scrambles letters in that string
%and displays the scrambled string
% written by Chris Kourtev 7/12/2010
clear all;
my_var = 'hello world';
mixstr = 'xxxxxxxxxxxxx';
disp(my_var);
for i = 1:length(mixstr)
mixstr(i) = my_var(ceil(rand*length(my_var)));
end;
disp(mixstr);

27. mat = [1, 5, 3; 2, 1, 5; 7, 9, 0] Vectors & Matrixes
A string is a list of characters
You can also have lists of numbers using vectors and matrixes
vect = [1, 2, 5, 6, 3]
mat = [1, 5, 3; 2, 1, 5; 7, 9, 0]
mat = [1, 5, 3; , 1, 5; , 9, 0]

28. mat = [1, 5, 3; 2, 1, 5; 7, 9, 0] Vectors & Matrixes 1 2 5 6 3 1 5 3 2
vect = [1, 2, 5, 6, 3] mat = [1, 5, 3; 2, 1, 5; 7, 9, 0]
mat = [1, 5, 3; , 1, 5; , 9, 0] 1 2 5 6 3
Vect
mat 1 5 3 2 7 9
note: vectors are basically 1 dimensional matrixes

29. Getting Values out of Vectors & Matrixes1 2 5 6 3
vect(3) returns 5
mat 1 5 3 2 7 9
mat(3,1) returns 7
Note: to get a cell you use (ROW, COLUMN)

30. vector as a 1D matrix
vect = [1; 2; 3] vect2 = vect’ 1 2 3 1 2 3

31. transposing mat 1 5 3 2 7 9 1 2 7 5 9 3 mat = if you set t_mat = mat’
if you set t_mat = mat’
t_mat(3, 1) is equal to mat(1,3)
Rows and columns are swapped
when you transpose a matrix
mat’ = 1 2 7 5 9 3

32. performing operations
vect + 3 vect + vect vect - 3 vect + [5, 4, 3] mat+mat’

33. multiply and divide
Don’t forget to put a dot before multiplication and division symbols
vect.*3
mat.*0.5
vect./2
vect2 = [2; 2; 4]
vect.*vect2
vect./vect2

34. task 2
Create a 6(rows)x4(columns) matrix filled with random integer values between 1 and 20
Create a zeroes matrix of the same dimensions
Replace each zero with a random number from the other matrix (as we did in the mix_strings program)
Display each value in the new mixed matrix
Hint 1: You will need to use nested loops
Hint 2: Look up how to use the “zeros” command
** Advanced task: Design your program so that it can work with matrices of any dimension just by changing the number of rows and column. Hint: Look up the “size” command