An Introduction to MATLAB. Lab tutor : Dennis Yang LIU Lab 1: Sept. 11, 2014

Transcription

1 Lab 1 of COMP 319 An Introduction to MATLAB Lab tutor : Dennis Yang LIU csygliu@comp.polyu.edu.hk Lab 1: Sept. 11,

2 Outline of Lab 1 Introduction to the Lab Matlab overview Basic manipulation in Matlab 2

3 Outline of Lab 1 Introduction to the Lab Matlab overview Basic manipulation in Matlab 3

4 Introduction to the Lab Schedule Date Lab 1 Sept. 11 (Thur.) and Sept. 16 (Tue.) Lab 2 Lab 3 Lab 4 Lab 5 Lab 6 Lab 7 Lab 8 Sept. 18 (Thur.) and Sept. 23 (Tue.) Sept. 25 (Thur.) and Sept. 30 (Tue.) Oct. 7 (Tue.) and Oct. 9 (Thur.) Oct. 14 (Tue.) and Oct. 16 (Thur.) Oct. 21 (Tue.) and Oct. 23 (Thur.) Oct. 28 (Tue.) and Oct. 30 (Thur.) Nov. 4 (Tue.) and Nov. 6 (Thur.) Lb9 Lab Nov. 11(T (Tue.) and dnov. 13(Th (Thur.) Lab 10 Lab 11 Lab 12 Nov. 18 (Tue.) and Nov. 20 (Thur.) Nov. 25 (Tue.) and Nov. 27 (Thur.) Dec. 2 (Tue.) and Dec. 4 (Thur.) 4

5 Introduction to the Lab Time and place of our labs Thur. 16:30 17:20 PQ 604B Tue. 09:30 10:20 PQ 606 The lab lbwill mainly il focus on Matlab lb Basic concepts and useful skills of Matlab (6 labs) Instructions to the lab project (6 labs: instructions and self-studies) Directory of lab material ml 5

6 Outline of Lab 1 Introduction to the Lab Matlab overview Basic manipulation in Matlab 6

7 Matlab Overview What is Matlab? Strengths of Matlab Weaknesses of Matlab 7

8 What is Matlab? Matlab MATrix LABoratory The name is derived from MATrix LABoratory. A programming language for doing numerical computation. Originally designed for solving linear algebra type problems using matrices (suitable for image and video processing). Functionality of Matlab built-in functions for solving problems requiring data analysis, signal processing, optimization, and several other types of scientific computations. also contains functions for 2-D and 3-D graphics and animation. 8

9 What is Matlab con t Considering i Matlab at thome Standard edition Available for roughly 2 thousand dollars Student edition Available for roughly 1 hundred dollars. Some limitations, such as the allowable size of a matrix 9

10 Strengths of Matlab Matlab bis relatively l easy to learn Matlab code is optimized to be relatively quick when performing matrix operations Matlab may behave like a calculator or as a programming language Matlab is interpreted, errors are easier to fix 10

11 Weaknesses of Matlab Mtlbi Matlab is an interpreted it tdl language (making itfor the most part slower than a compiled language such as C) Matlab is NOT a general purpose programming language Matlab is designed for scientific computation and is not suitable for some things (such as parsing text) 11

12 Outline of Lab 1 Introduction to the Lab Matlab overview Basic manipulation in Matlab 12

13 Basic manipulation of Matlab Opening and closing Matlab The Matlab user interface M-file building, saving and running 13

14 Opening and closing Matlab Opening Matlab (for Windows XP): Single click Start, then Single click Run, then Input nalwin32, then Double click COMP, then Double click Network Application Packages, then Double click Statistical & Mathematical, then Double click Matlab Select one version (e.g., R2012a), double click to open 14

15 Opening and closing Matlab Opening Matlab (for Windows 7): Single click Start, then Single click Computer, then Double click disk Y, then Double click Win32, then Double click Matlab Select one version (e.g., R2012a), then Double click matlab.exe to open Closing Matlab Type exit or quit at the Matlab prompt; or Click the close icon x in the top-right corner of the screen 15

16 Matlab user interface Workspace Command Window Command History 16

17 Matlab user interface con t Command Window type commands Workspace view program variables clear to clear double click likon a variable ibl to see itin the Array Editor Command History view past commands 17

18 Using the Command Window Do it yourself 1. To compute the value of 5 2, type this command: >> 5^2 The following output will be displayed: ans = To find the cosine of pi, type: >> cos(pi) which result in the following output: ans = -1 Note: ans is the default variable name given by Matlab. 18

19 Using the Command History Do it yourself In the command window, type: >> clc This will clear the command window but leave the data in the command history. Try double-click: cos(pi) This will result in the following display in the command window: ans = -1 19

20 Using the Workspace Do it yourself Enter the following two-dimensional matrix in the command window: >> c= [1,2,3,4; 10,20,30,40; 5,10,15,20]; c should now be listed in the workspace window. Double clik it. An array editor will be listed above the command window. Then you can add or change values in the array editor. 20

21 Some useful notes The Matlab environment is command oriented somewhat like UNIX. Aprompt(>>) appears on the screen and a Matlab statement can be entered. When the <ENTER> key is pressed, the statement is executed, and another prompt appears. If a statement is terminated with a semicolon ( ; ), no results will be displayed. Otherwise results will appear before the next prompt.» a=5;» b=a/2 b = » 21

22 Some useful notes con t In Matlab, the equal sign ( = ) is used to assign values to the variables. It does not mean equal to. In Matlab environment, equal to is expressed by two consecutive equal signs ( == ). >> x = 5 means that assigning the value 5 to the variable x. >> x == y means that the value of x is equal to the value of y. 22

23 Some useful notes con t Matlab Variable Names Variable names are case sensitive Variable names can contain up to 63 characters (as of Matlab 6.5 and newer) Variable names must start with a letter followed by letters, digits, and underscores. 23

24 Some useful notes con t Matlab has some special (reserved) words that you may not use for end if while function return elseif case otherwise switch continue else try catch global persistent break 24

25 Matlab Help Different ways to find information help help general, help mean, sqrt... click help p icon Search information from the internet via google 25

26 Matlab Help 26

27 Some other useful Matlab commands who List known variables whos List known variables plus their size clear x y Clear variables x and y from workspace clear Clear all variables from workspace clc Clear the command window 27

28 M-file building and saving The command window offers an environment similar to a scratch pad. Using the command window allows you to save the values you calculate, but not the commands used to generate those values. If you want to save the command sequence, you will need to use the edit window to create an M-file. 28

29 M-file building (step 1) File - New - Script 29

30 M-file building (step 2) 30

31 M-file building (step 3) An simple example: 31

32 Explanation of the example Line 1: instructs Matlab to delete all variables in the working directory. Line 2: instructs Matlab to clear the command window. Any text that now appears in the command window will be the result of running this M-file, not the result of previous activities. Line 3: blank lines help improve the readability of a M-file. Line 4 and 5: Assign values to A and B. The semicolon prevents Matlab from displaying the result in the command window; the percent sign begins the legible comment. Line 6: Intermediate results with suitable names sometimes improve the legibility of the algorithm. Line 7: Invokes the built-in function sqrt() to compute the final result. 32

33 File - Save M-file saving (step 1) 33

34 M-file saving (step 2) Type hypo as the file name, then click Save 34

35 Run M-file (method 1) Type the M-file s name: hypo into command window and then press the enter key. 35

36 Run M-file (method 2: step 1) 36

37 Run M-file (method 2: step 2) Double click the file hypo ; Or single click the file hypo and single click open 37

38 Run M-file (method 2: step 3) 38

39 Run M-file (method 2: step 4) 39

40 Summary of Lab 1 Introduction to the Lab Matlab overview What is Matlab? Strengths and weaknesses of Matlab Basic manipulation in Matlab Start and quit Matlab The Matlab user interface M-file building, saving and running 40

41 Next class 1. Vectors 2. Arrays 3. Built-in i functions 4. Some exercises 41