% CMSC 426

help 

help plus

demo

% Simple interpreted commands

help ops

7+3

8-2

2^7

sqrt(17*3^2)

x = 7;

y = 8;

x*y

% Notice difference between:

z = x*y;

% and 

z

% Making a vector

x = [1 2 3 4]

% or 

y = 1:4;

% or 

y1 = [y,y]

% Making a column vector

z = [1; 2; 3; 4]

% or 

z = x'

% What happens when we do:

[y, z]

% Indexing into vectors

x(2)

x(2:3)

x(2:4)

% Adding vectors

x + (3:6)

% Scaling vectors

7*x

% Vector operations

sum(x)

max(x)

x.^2

y = x/(sqrt(sum(x.^2)))

% Inner products

theta1 = pi/4;
theta2 = pi/8;

u = [cos(theta1); sin(theta1)]
v = [cos(theta2); sin(theta2)]

u'*v

cos(pi/8)

% Matrices

A = [1, 2, 3; 4, 5, 6]

B = [1, 0, 1; 0, 1, 0]

% Note

[A,A]

[B;[7, 6, 5]]

A+B

C = [7, 2; 3, 1]

C*A

A*C

I = eye(2)

C

C*I

D = [4, 0; 4, 5]

A

A'

C

C'

det(C)

C

inv(C)

inv(C)*C

C*inv(C)

% Indexing

A

A(2,1)

A(2,1:2)

A(2,:)

% Geometric transformations

% translation

Q = [0, 0, 1, 1; 0, 1, 0, 1];

figure

plot(Q(1,:), Q(2,:), 'o', 'LineWidth', 6)

Q = [Q; ones(1,4)]

T = [1, 0, -.5; 0, 1, 1]

Qt = T*Q

hold on

plot(Qt(1,:), Qt(2,:), 'o', 'LineWidth', 6)

hold off

% rotation

Q = [0, 0, 1, 1; 0, 1, 0, 1];

figure

plot(Q(1,:), Q(2,:), 'o', 'LineWidth', 6)

R = [cos(pi/4), -sin(pi/4); sin(pi/4), cos(pi/4)];

R*R'

Qr = R*Q

hold on

plot(Qr(1,:), Qr(2,:), 'ok', 'LineWidth', 6)

hold off

T = rand(2,2)

[r1, s, r2] = svd(T)

T

r1*s*r2

r1*r1'

s

% Files

pwd

ls

path

help addpath

% Look at function test

test(3,4)

% Images

dog = imread('dog1.jpg');

figure

imshow(dog);

dogbw = rgb2gray(dog);

figure

imshow(dogbw);

imshow(imrotate(dogbw,45,'bilinear'));

% iteration

for i = 1:5 i, end

% We can zoom in on the nose

figure; imshow(dogbw(120:240, 150:270))

% Look at the raw pixel values.

for i = 170:190, for j=200:220, fprintf(1,'%3.3d ', double(dogbw(i,j))); end, fprintf(1,'\n'); end

dogbw(170:200,215)'

% or plot them.

figure

plot(dogbw(170:200,215))

size(dog)