Introduction%20to%20MATLAB

1
Introduction to MATLAB

• Northeastern University College of Computer and
  Information Science
• Co-op Preparation University (CPU)

10/22/2003
2
Overview for 10/22/2003

• Review of topics covered in last session
  (10/20/2003)
• Review of the MATLAB environment (covered in last
  session)
• Declaring and manipulating variables
• Useful functions

3
Review of 10/20/2003

• Contact Information
• Course Overview
• MATLAB Overview

4
Contact Information

• E-mail wmason_at_ccs.neu.edu
• Office Hours Wednesday after class
• Some information available
• http//www.ccs.neu.edu/home/wmason

5
Course Overview

• Course Structure

6
Course Structure

• Week 1 Overview of MATLAB
• History of MATLAB
• Overview of MATLAB environment
• Discussion of MATLAB in co-op
• Week 2 Basic MATLAB
• Simple MATLAB functionality
• Syntax, Commands
• Exercises involving basic MATLAB functionality

7
Course Structure, cont 2

• Week 3 Advanced MATLAB Functionality
• Beyond MATLAB as a calculator
• The MATLAB programming language
• Project showcasing MATLABs advanced functionality

8
Meeting Times and Locations

• Week 1
• Class 1
• Monday, Oct. 20, 6 - 7 p.m., 257 CN
• Class 2
• Wednesday, Oct. 22, 6 - 7 p.m., 257 CN
• Class 3
• Thursday, Oct. 23, 6 - 7 p.m., 247 CN

9
Meeting Times and Locations, cont 2

• Week 2
• Class 1
• Monday, Oct. 27, 6 - 7 p.m., 257 CN
• Class 2
• Wednesday, Oct. 29, 6 - 7 p.m., 257 CN
• Class 3
• Thursday, Oct. 30, 6 - 7 p.m., 247 CN

10
Meeting Times and Locations, cont 3

• Week 3
• Class 1
• Monday, Nov. 3, 6 - 7 p.m., 257 CN
• Class 2
• Wednesday, Nov. 5, 6 - 7 p.m., 257 CN
• Class 3
• Thursday, Nov. 6, 6 - 7 p.m., 247 CN

11
Coursework

• Collection of exercises
• Will occur during the second week
• Will involve MATLABs basic functionality
• Final project
• Will occur during the final two sessions
• Will cover MATLABs basic and advanced
  functionality

12
History of MATLAB

• Ancestral software to MATLAB
• Fortran subroutines for solving linear (LINPACK)
  and eigenvalue (EISPACK) problems
• Developed primarily by Cleve Moler in the 1970s

13
History of MATLAB, cont 2

• Later, when teaching courses in mathematics,
  Moler wanted his students to be able to use
  LINPACK and EISPACK without requiring knowledge
  of Fortran
• MATLAB developed as an interactive system to
  access LINPACK and EISPACK

14
History of MATLAB, cont 3

• MATLAB gained popularity primarily through word
  of mouth because it was not officially
  distributed
• In the 1980s, MATLAB was rewritten in C with
  more functionality (such as plotting routines)

15
History of MATLAB, cont 4

• The Mathworks, Inc. was created in 1984
• The Mathworks is now responsible for development,
  sale, and support for MATLAB
• The Mathworks is located in Natick, MA
• The Mathworks is an employer that hires co-ops
  through our co-op program

16
MATLAB GUI

• Launch Pad / Toolbox
• Workspace
• Current Directory
• Command History
• Command Window

17
Launch Pad / Toolbox

• Will not be covered
• Launch Pad allows you to start help/demos
• Toolbox is for use with specialized packages
  (Signal Processing)

18
Workspace

• Allows access to data
• Area of memory managed through the Command Window
• Shows Name, Size (in elements), Number of Bytes
  and Type of Variable

19
Current Directory

• MATLAB, like Windows or UNIX, has a current
  directory
• MATLAB functions can be called from any directory
• Your programs (to be discussed later) are only
  available if the current directory is the one
  that they exist in

20
Command History

• Allows access to the commands used during this
  session, and possibly previous sessions
• Clicking and dragging to the Command window
  allows you to re-execute previous commands

21
Command Window

• Probably the most important part of the GUI
• Allows you to input the commands that will create
  variables, modify variables and even (later)
  execute scripts and functions you program
  yourself.

22
Simple Commands

• who
• whos
• save
• clear
• load

23
who

• who lists the variables currently in the
  workspace.
• As we learn more about the data structures
  available in MATLAB, we will see more uses of
  who

24
whos

• whos is similar to who, but also gives size and
  storage information
• s whos(...) returns a structure with these
  fields name variable name size variable size
  bytes number of bytes allocated for the array
  class class of variable and assigns it to the
  variable s. (We will discuss structures more).

25
Save

• save saves workspace variables on disk
• save filename stores all workspace variables in
  the current directory in filename.mat
• save filename var1 var2 ... saves only the
  specified workspace variables in filename.mat.
  Use the wildcard to save only those variables
  that match the specified pattern.

26
Clear

• clear removes items from workspace, freeing up
  system memory
• Examples of syntax
• clear
• clear name
• clear name1 name2 name3 ...

27
clc

• Not quite clear
• clc clears only the command window, and has no
  effect on variables in the workspace.

28
Load

• load - loads workspace variables from disk
• Examples of Syntax
• load
• load filename
• load filename X Y Z

29
Declaring a variable in MATLAB

• Not necessary to specify a type. (Such as int or
  float)
• Several kinds of variables
• Vector
• Matrix
• Structure
• Cell array

30
Declaring a variable, cont 2

• For an integer or floating point number simply
  set a variable name equal to some character
• Ex. A 5
• Or A 5

31
Sidenote 1

• The presence or lack of a semi-colon after a
  MATLAB command does not generate an error of any
  kind
• The presence of a semi-colon tells MATLAB to
  suppress the screen output of the command

32
Sidenote 1, cont 2

• The lack of a semi-colon will make MATLAB output
  the result of the command you entered
• One of these options is not necessarily better
  than the other

33
Declaring a variable, cont 3

• You may now use the simple integer or float that
  you used like a normal number (though internally
  it is treated like a 1 by 1 matrix)
• Possible operations
• , -, /
• Many functions (round(), ceil(), floor())

34
Declaring a variable, cont 4

• You may also make a vector rather simply
• The syntax is to set a variable name equal to
  some numbers, which are surrounded by brackets
  and separated by either spaces or commas
• Ex. A 1 2 3 4 5
• Or A 1,2,3,4,5

35
Declaring a variable, cont 5

• You may also declare a variable in a general
  fashion much more quickly
• Ex. A 1110
• The first 1 would indicate the number to begin
  counting at
• The second 1 would be the increase each time
• And the count would end at 10

36
Declaring a variable, cont 6

• Matrices are the primary variable type for MATLAB
• Matrices are declared similar to the declaration
  of a vector
• Begin with a variable name, and set it equal to a
  set of numbers, surrounded by brackets. Each
  number should be seperated by a comma or
  semi-colon

37
Declaring a variable, cont 7

• The semi-colons in a matrix declaration indicate
  where the row would end
• Ex. A 1,23,4 would create a matrix that
  looks like
• 1 2
• 3 4

38
Declaring a variable, cont 7

• Matrices may be used as normal variables now.
  Multiplying is already defined for matrices, and
  additional code does not need to be written.

39
Declaring a variable, cont 8

• The final type of variable we will discuss today
  will be a struct.
• The command struct is used to create a structure
• Syntax
• s struct('field1',,'field2',,...)
• s struct('field1',values1,'field2',values2,...)

40
Declaring a variable, cont 9

• A simple declaration of a structure is as
  follows
• Student.name Joe
• Student.age 23
• Student.major Computer Science

41
Declaring a variable, cont 10

• Arrays of structures are possible.
• Taking the previous example, if one were to
  write
• Student(2).name Bill
• etc
• Then the array would be created for you.

42
Declaring a variable, cont 11

• Structures can group information, but methods are
  not written for them.

43
End
Another satisfied MATLAB user!