1. Introduction to MATLAB
Morris Law
March 21, 2018

2. Outline Matlab software Entering matrix
Matrix function and manipulation
Matlab graphics
Matlab programming: writing M-file and functions
Function input & output
Control flow

3. MATLAB software Multi-platforms (Windows, Linux, MacOSX)
Technical computing
Script language
Variables are all matrices
Expandable by adding toolboxes

4. Entering matrix Explicit listing M-file External data files
Stored the above statement in ex1.m. Run the M-file, i.e. >> ex1
External data files
>> load A.dat
Built-in statements and functions
>> B = eye(3)

5. Matrix function and manipulation
ones(3), zeros(3), eye(3)
magic(4), hilb(5), rand(4,3)
size(A), eig(A), det(A), inv(A), diag(A)
sum(A), prod(A), mean(A), max(A), std(A)

6. Exercise on Matrix functions
Try
A = [1 2 3; 4 5 6; 7 0 9]
x = ones(3)
y = eye(3)
z = zeros(3)
d = diag(A)
det(A)
inv(A)
rank(A)
eig(A)

7. Exercise on Matrix functions
m = magic(4)
sum(m)
sum(m’)
sum(diag(m))
r = rand(4,3)
size(r)

8. Matrix elements >> x = [-1.3, sqrt(3), (1+2+3)*4/5 ];
>> x(5)= abs(x(1))
x =
>> y = 1:5
y =
xy = [x;y]
xy =

9. Matrix elements (cont)
>> B = [A;r];
>> C = [A,zeros(size(A));ones(size(A)),A]
C =
>> D = C(1:3,:)
>> D = C(:,3:4)

10. Matrix Arithmetic Additions (+) Subtraction (-) Multiplication (*)
Right division (/)
Solve A = xb by x = A/b
Left division (\)
Solve Ax = b by x = A\b
Power (^)

11. Element-by-Element Operation
Using Period (.)
x = [1,2,3]; y = [4 5 6];
>> x .* y
ans
>> x ./ y
>> x .\ y
>> x .^ y
ans
>> x .^ 2
>> 2 .^ [x y]

12. MATLAB graphics If y is a vector, plot(y) produced a linear graph
plot(x,y) produces a graph of y versus x
t = 0: pi/10: 2*pi;
x = sin(t)
Y1 = sin(t+.25);
Y2 = sin(t+.50);
plot(x,y1,’r-’,x,y2,’g--’)
Title(‘Phase Shift’)
xlabel(‘x=sin(t)’);
ylabel(‘y1=sin(t+)’);

13. MATLAB graphics – 3D mesh
The following commands draw a mesh
x = [-pi:0.1:pi]; y=x;
[X,Y]=meshgrid(x,y);
Z = sin(X).* sin(Y) + cos(X).*cos(Y);
mesh(Z);
#surf(Z);
#contour(Z);

14. MATLAB programming Two kinds of MATLAB program 1. Script or M-file
sequence of Matlab statements
without input and output
variables are global
2. Functions
with input and output defined as
function [out1, out2, … outN]= funcname(in1, in2, … inN)
variables are local

15. Writing scripts / M-files
Use Matlab M-file editor, save the following as fibo.m
% An M-file to calculate Fibonacci numbers
f = [1 1]; i=1;
while f(i) + f(i+1) < 1000
f(i+2) = f(i) + f(i+1);
i=i+1;
end
plot(f);
At the Matlab command prompt, type the following to run
>> fibo

16. Writing script – another example
looptest.m
% Fill b with square roots of 1 to 1000 using a for loop
clear;
tic;
for i= 1:1000
b(i) = sqrt(i);
end
t=toc;
disp([‘Time taken for loop method is ‘, num2str(t)]);
% Fill b with square roots of 1 to 1000 using a vector
a = 1:1000;
b = sqrt(a);
disp([‘Time taken for vector method is ‘, num2str(t)]);
Run the program with
>> looptest

17. MATLAB function MATLAB functions allow input and output variables
function y = stat(x)
% mean average
[ m n ] = size(x);
if m == 1
m = n;
end
y = sum(x) / m;
If z is a vector, z = 1:99, type
>> mean(z)
ans 50

18. Control flow If and break statement For Loops While Loops or
for v = expression
statements
end
While Loops
while expression
If and break statement
if expression, break, end or
if expression
statements
[elseif expression
statements]
[else expression
end

19. General Purpose commands (1/5)
Managing commands and functions
demo run demo
help on line documentation
Info information about MATLAB and MathWorks
lookfor keyword search through the help entries
path control MATLAB's search path
type list M-file
what directory listing of M-, MAT- and MEX-files
which locate functions and files

20. General Purpose commands (2/5)
Managing variables and the workspace
clear clear variables and functions from memory
disp display matrix or text
length length of vector
load retrieve variables from disk
pack consolidate workspace memory
save save workspace variables to disk
size size of matrix
who list current variables
whos list current variables, long form

21. General Purpose commands (3/5)
Working with files and the operating system
cd change current working directory
delete delete file
diary save text of MATLAB session
dir directory listing
getenv get environment value
! execute operating system command

22. General Purpose commands (4/5)
Controlling the command window
clc clear command window
echo echo commands inside script files
format set output format
home send cursor home
more control paged output in command window

23. General Purpose commands (5/5)
Starting and quitting from MATLAB
matlabrc master startup M-file
quit terminate MATLAB
startup M-file executed when MATLAB is invoked

24. Search for documentation
helpdesk

25. Reference Booklet on Introduction to MATLAB MATLAB primer (version 3)
MATLAB primer (version R2017b)