A tutorial for MATLAB.

1. MATLAB

2. Matalb
• =>
• =>
• => i.e. integer -> double
•
•

3. toolbox
toolbox
toolbox

4. Matlab

5. Matlab
current
folder
variablecommand line

6. command
• lookfor <keyword>
• help <command>
• a=1
• a=2;
• whos a
• clear 0
• %

7. simple calculator
• a = 1
• b = a+1
• c = a + b
• d = a*b^c - c/b

8. predefined variables
• pi %=> 3.14……
• i or j %=> 0.0000+1.0000i
• %Tips: use 1i

9. variable declaration
• s => undefined
• scalar: s=1
• vector:
• v1=[1,2,3]
• v1=1:3
• v2=[1;2;3]
• v2=[1,2,3]'
• matrix
• m1=[1,2;3,4]
1 2
3 4
row 1
row 2
col 1 col 2

10. vector indexing
• v=1:2:10
• v(5)
• v(1:3)
• v(:)
• v(end)
• v(1:end~=3)
• Try it:
• Get the 2nd element
from v.
• Get 3rd to end
elements.
• Put 1st, 3rd, 5th
element as a new
array named b.

11. matrix indexing
• matrix
• m=[1:3;4:6;7:9]
1 2 3
4 5 6
7 8 9
• matrix
• m=[1:3;4:6;7:9]
• m(1,:) % get 1st row
• m(:) % get all
element
• m(1:2,3) % submatrix
• m(8) ???
• linear indexing
• m([1,4,5,6])

12. try it
• m = magic(5)
• Get first column from m.
• Get 3~5 rows from m.
• Get submatrix which formed by the intersection of 1~3
rows and 2~4 columns of m and store in a new matrix
m1(3x3 matrix).
• Get a column vector which formed by all the odd linear
index elements in m.

13. operator
• matrix operatior
• *
• /
• ^
• …..
• element-wise operator
• .*
• ./
• .^
• …..

14. try it
• v1=1:3
• v2=v1'
• v3=v1*2
• v3*v2
• v2*v3
• v1.*v3
• v1.^v3
• m1=[1:3;4:6]
• m2=m1'
• m3=m1*2
• m3*m2
• m2*m3
• m1.*m3
• 10.^m1

15. matlab function
• v=1:20;
• sin(v)
• cos(v), tan(v)….
• exp(v), log(v)…
• diag, eig( )
• sum( )
• check how to use: help <function>

16. try it
• m = magic(100);
• Get following arrays:
• 1st row
• 25th column
• diagonal
• Get the summation of above arrays. Are they the
same?

17. example 1:
eigenvalue problem
• A=magic(5)
• [vectors, values] = eig(A)
• isequal(A*vectors,vectors*values) %=> ?
• A*vectors-vectors*values %=> ?

18. example 2:
make a plot
• linspace(<start>,<end>,<sep>)
• x = linspace(0,2*pi,100);
• y = sin(x);
• figure;
• plot(x,y);
• y2 = cos(x);
• plot(x,y,x,y2);

20. BUT !!!

22. plot cont.
• plot(x,y,x,y2,'LineWidth',2);
• title('AM2
plot','FontWeight','bold','FontSize',20);
• axis tight;
• xlabel('x','FontWeight','bold','FontSize',20);
• ylabel('y','FontWeight','bold','FontSize',20);
• set(gca,'XTick',[0 pi 2*pi],'XTickLabel',
{'0','pi','2pi'});
• set(gca,'FontWeight','bold','fontsize',20);

24. compare two scalar
• ==
• >
• <
• >=
• <=
• true: return 1
• otherwise: return 0
• Try it
• 1==2
• 3>=2
• 1>=2
• 3<3

25. if…else
• grade = 65;
• if grade >= 60
• disp('Pass~');
• else
• disp('Fail!! QQ~');
• end

26. for loop
• grades = [60,50,40,70];
• names = {'John','Peter','Chen','Lucky'};
• for i=1:numel(grades)
• if grades(i) >= 60
• disp([names(i) ': Pass']);
• else
• disp([names(i) ': Fail']);
• end
• end

27. try it
• m = magic(100);
• Get row index and column index (i,j) for all the
elements which grater than 3.

28. some tips for speed up
•
• zeros(n,m)
• for loop
• tic;toc; %timer
• JIT compiler
•
• logical array find

29. N = 1e7;
tic
w = zeros(1, N);
for i = 1:N
w(i) = i*5;
end
fprintf('For loop: %.4fsn', toc);%=> 0.053s
tic
y = (1:N)*5;
fprintf('Vectorized: %.4fsn', toc);%=> 0.082s
Try it:
feature(‘accel’,’off’);
and run again

30. parfor
N = 1e7;
tic
w = zeros(1, N);
parfor i = 1:N
w(i) = i*5;
end
fprintf('Parfor loop: %.4fsn', toc);
%=> 1.853s

31. homework
• matlab
• id =
• id_last = id
• y=5sin(2/id_last*x) 2
• x 0 10pi 500
•
• AM2 MATLAB <id>
• x 0 10pi pi
• 20
• ceiba

32. example