Colorado School of Mines
Computer Vision
Professor William Hoff
Dept of Electrical Engineering &Computer Science
Colorado School of Mines
Computer Vision
http://inside.mines.edu/~whoff/
1
Introduction to Matlab
Colorado School of Mines
Computer Vision
Matlab Introduction
• Overview
– “Matrix Laboratory”
– An interactive programming environment
– http://www.mathworks.com
• Availability
– On computers in BB 316, 304, 305 (you need an “adit” logon)
– Student version available
• Why we are using
– Easy to prototype
– Powerful toolboxes such as the image processing toolbox
– Widely used; good help and documentation
Colorado School of Mines
Computer Vision
3
Matlab
• Programming
–
–
–
–
Can type on command line, or use a program file (“m”‐file)
Semicolon at end of line is optional (suppresses printing)
Control flow (if, for, etc) similar to C
Differences from C: no variable declarations, no pointers
• Help
– Help browser ‐ best source
– Command line
– Web (http://www.mathworks.com/access/helpdesk/help/techdoc/matlab.s
html)
– Pointers to tutorials: http://people.duke.edu/~hpgavin/matlab.html
Colorado School of Mines
Computer Vision
4
Matlab
• Everything is a matrix
– a variable is a 1x1 matrix
• Initializing a matrix:
– Example: my_matrix = [1 2 3; 4 5 6; 7 8 9];
• Accessing a matrix (row, column):
– my_matrix(1,2) has the value 2
• Colon operator generates a range
my_matrix =
1 2 3
4 5 6
7 8 9
– Example: 1:10 = [1 2 3 4 5 6 7 8 9 10]
– mytest(1, 2:4) is equivalent to mytest(1,[2 3 4])
– mytest(3, :) refers to all elements of row 3
Colorado School of Mines
Computer Vision
5
Matlab
•
Built‐in functions (exp, sin, log, etc)
•
Variables
– whos (view all variables)
– clear all (Clear all variables )
•
Types
– double (default)
– Also have integer, unsigned integer, logical, complex
•
Expressions
–
–
–
–
•
+,‐,/,*
Power is ^
Transpose is ‘ (apostrophe)
Period indicates point‐by‐point operation Plotting example (sin)
Colorado School of Mines
Computer Vision
6
Exercises
• Create a vector A, consisting of the first 5 odd numbers
• Create a vector B, consisting of the first 5 even numbers
• Find the inner (dot) product of A and B
Colorado School of Mines
Computer Vision
7
Exercises
• Find C, the outer product of A and B
– what is the size of C ?
• Compute the sum of all the elements of C
• Compute the trace of C
• Compute the determinant of C
• Square all the elements of C
Colorado School of Mines
Computer Vision
8
Exercises
• Create a “magic square” matrix M, having the same size as C (see help on the function magic)
• Compute the matrix product of M and C
• Compute the point‐by‐point product of M and C
• Compute the product of M and (column) vector A
Colorado School of Mines
Computer Vision
9
Exercises
• Write a program (using “for” loops) to compute the first 100 Fibonacci numbers
– Recall the recurrence relation to generate them:
• F0 = 0, F1 = 1
• Fn = Fn‐1 + Fn‐2
Colorado School of Mines
Computer Vision
10
Exercises
• Plot x vs ln(x), for values of x from 0 to 10
Colorado School of Mines
Computer Vision
11