© 2 0 1 2 M a t h W o r k s , I n c .

MATLAB^® Fundamentals

MATLAB FUNDAMENTALS ^&

PROGRAMMING TECHNIQUES

© 2012 MathWorks, Inc.

Pony Lai

support@terasoft.com.tw

MathWorks ...at a Glance

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Simulink Product Family Application-Specific Products

MathWorks Product Overview

MATLAB Product Family

Diverse Users

Signal processing

& communications

Utilities & energy

Biotech, medical,

& pharmaceutical

Education Aerospace

& defense

Finance & economics

Government Instrumentation

Automotive

What Can You Do with MATLAB ?

Interactively import, analyze, and export data

Perform calculations and analysis on data sets

01/95 01/00 01/05

2 2.5 3 3.5 4 4.5 5

Date Retail consumption [109 kWh/day]

10⁰ 10¹

10^-3 10^-2 10^-1 10⁰ 10¹ 10² 10³

Period [years]

Power

01/95 01/00 01/05

1.5 2 2.5 3 3.5 4 4.5 5

Date Retail consumption [109 kWh/day]

Data 8-term Model

Create informative data visualizations Write programs to automate complex tasks analysis on data sets

Mexico

Mexico data?

??? Error using ==> gpif at 21 No data for Mexico

No

Yes

19901 1992 1994 1996 1998 2000 2002 2004 2006 2008 1.5

2 2.5

Year

Mexico prices

-102 -100

-98 -96

-94

30 32 34 36 0.07 0.08 0.09 0.1

Lat. Lon.

O3 [ppm]

Course Outline

● Working with the MATLAB User Interface

● Variables and Expressions

● Automating Commands with Scripts

● Automating Commands with Scripts

● Working with Data Files

Course Outline

● Working with the MATLAB User Interface

● Variables and Expressions

● Automating Commands with Scripts

● Automating Commands with Scripts

● Working with Data Files

Outline

• Reading data from file

• Saving and loading variables

• Plotting data

• Plotting data

• Customizing plots

• Calculating statistics and best-fit line

• Exporting graphics for use in other applications

The MATLAB Desktop

Variables (data) in memory Desktop controls

Current folder

memory

Previously entered commands Commands entered

& results returned Files in the

current folder

Customizing the Desktop

Window

actions Resize &

actions Resize &

reposition

Course Example: Gas Price Data

C:\class\coursefiles\mlbe\gasprices

Interactive Importing

Variables in the Base Workspace

19

1990 NaN 1.87 3.63 2.65 4.59 3.16 1 2.05 2.82 1.16 1991 1.96 1.92 3.45 2.9 4.5 3.46 1.3 2.49 3.01 1.14 1992 1.89 1.73 3.56 3.27 4.53 3.58 1.5 2.65 3.06 1.13 1993 1.73 1.57 3.41 3.07 3.68 4.16 1.56 2.88 2.84 1.11 1994 1.84 1.45 3.59 3.52 3.7 4.36 1.48 2.87 2.99 1.11 1995 1.95 1.53 4.26 3.96 4 4.43 1.11 2.94 3.21 1.15 1996 2.12 1.61 4.41 3.94 4.39 3.64 1.25 3.18 3.34 1.23 1997 2.05 1.62 4 3.53 4.07 3.26 1.47 3.34 3.83 1.23 1998 1.63 1.38 3.87 3.34 3.84 2.82 1.49 3.04 4.06 1.06 1999 1.72 1.52 3.85 3.42 3.87 3.27 1.79 3.8 4.29 1.17 2000 1.94 1.86 3.8 3.45 3.77 3.65 2.01 4.18 4.58 1.51 2001 1.71 1.72 3.51 3.4 3.57 3.27 2.2 3.76 4.13 1.46 2002 1.76 1.69 3.62 3.67 3.74 3.15 2.24 3.84 4.16 1.36 2003 2.19 1.99 4.35 4.59 4.53 3.47 2.04 4.11 4.7 1.59 2004 2.72 2.37 4.99 5.24 5.29 3.93 2.03 4.51 5.56 1.88 2005 3.23 2.89 5.46 5.66 5.74 4.28 2.22 5.28 5.97 2.3 2006 3.54 3.26 5.88 6.03 6.1 4.47 2.31 5.92 6.36 2.59 2007 3.85 3.59 6.6 6.88 6.73 4.49 2.4 6.21 7.13 2.8 2008 4.45 4.08 7.51 7.75 7.63 5.74 2.45 5.83 7.42 3.27

11

numeric data
“double precision”

The Variable Editor

New Variables

Saving and Loading Variables

Plotting the Data

Plot Tools

Axis labels -2 Units -1

4/10 Units -1

Change properties

Select plot components Add plot

elements

Multiple Plots

1

3

2

Formatting the Plot

Data Statistics Tool

Basic Fitting Tool

Exporting to Another Application

Shortcuts

Test Your Knowledge

1. Where does MATLAB display a listing of stored variables and associated attributes?

A. Command Window B. Workspace browser

C. Current Directory browser D. Command History

D. Command History

2. The default MATLAB variable type is:

A. Single B. Double C. Cell

3. T/F: The MATLAB desktop is customizable.

Course Outline

● Working with the MATLAB User Interface

● Variables and Expressions

● Automating Commands with Scripts

● Automating Commands with Scripts

● Working with Data Files

Outline

6 5 4

3 2 1

• Entering commands

• Creating variables & Data Type

• Getting help

9 8 7

6 5

• Getting help 4

• Accessing and modifying values in variables

• Creating character variables

MATLAB Commands

Saving and Loading MAT-Files

save

load

Assignment

>> no_of_penguins = x*sin(pi*t);

1. evaluate right-hand side 2. assign resulting value to

variable on left-hand side create new variable or

overwrite old one, as appropriate

MATLAB Data Types

Array

[full or sparse]

logical char numeric cell structure user

class function handle

Scalar

int8, uint8, int16, uint16, int32, uint32, int64, uint64

single double

abc

Boolean Operating and Indexing

>> Mass = [-2 10 NaN 30 -11 Inf 31];

>> each_pos = Mass>=0 each_pos =

0 1 0 1 0 1 1

>> all_pos = all(Mass>=0) all_pos =

0 Boolean Operators

= = equal to

> greater than

< less than

~= not

0

>> pos_fin = (Mass>=0)&(isfinite(Mass)) pos_fin =

0 1 0 1 0 0 1

>> good_mass = Mass(pos_fin) good_mass =

10 30 31

& and

| or isempty()

isfinite(), etc. . . . any()

all()

1 = TRUE 0 = FALSE

>> bool_ops

Integer Arrays

How many colors of truck could you possibly need?

256*256*256

= 16.8 million

double uint8

Creating Vectors

n subdivision points

>> x = [2,3,5,7,11,13];

Arbitrary data

Equally-spaced values

a

n subdivision points

b dx

>> x = a:dx:b;

>> x = linspace(a,b,n);

x

Creating Matrices

>> A = [1,2,3; 4,5,6; 7,8,9];

>> A = [1 2 3; 4 5 6; 7 8 9];

or

or

>> A = [1 2 3 4 5 6

7 8 9]

or

data entry mode

9 8 7

6 5 4

3 2 1

Matrix Creation Functions

eye

gallery hadamard hankel hilb

invhilb magic ones ones pascal rand randi randn rosser toeplitz vander

wilkinson zeros

 

 





 

 





 

 





B bar

foo 1 2

0 0 1 14

. 3 Cell Arrays

>> A = {pi,[],'foo';...

'bar',eye(2),2;...

[],B,[]};

>> A{2,2}(:,2) ans =

0 1

Construc t

Access

 

  B

Characters and Strings

>> MarkA = 'Friends, Romans, countrymen, lend me your ears';

>> y = x

>> y = 'x'

variable character

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

'F' 'r' 'i' 'e' 'n' 'd' 's' ',' ' ' 'R' 'o' 'm' 'a' 'n' 's' ',' ' ' 'c'

1-by-46 char array

>> FriendNationality = MarkA(10:15)

Fields

MyWhale

fundamental frequency amplitude

175 2

name ^Mushu

Structures

Fields

[x,t] = callmodel_fun_s(MyWhale);

decay rate ^1.5

modulation frequency number of harmonics

0.65 3

aquarium(3)

fundamental frequency amplitude

decay rate

165

1 0.8

name ^Shamu

aquarium(2)

name ^Willy

>> aquarium aquarium =

1x3 struct array with fields:

name

fundamentalfreq amplitude

decayrate

modulationfreq harmonics

Structure Arrays

decay rate ^0.8

modulation frequency number of harmonics

1.0 4

fundamental frequency amplitude

decay rate

180

2.5 1.9

modulation frequency number of harmonics

0.5 5

aquarium(1)

fundamental frequency amplitude

decay rate

175

2 1.5

name ^Mushu

modulation frequency number of harmonics

0.65 3

aquarium(3)

fundamental frequency amplitude

decay rate

165

1 0.8

name ^Shamu

aquarium(2)

name ^Willy

Indexing into Structure Arrays

>> aquarium(2)

>> aquarium.amplitude

decay rate ^0.8

modulation frequency number of harmonics

1.0 4

fundamental frequency amplitude

decay rate

180

2.5 1.9

modulation frequency number of harmonics

0.5 5

aquarium(1)

fundamental frequency amplitude

decay rate

175

2 1.5

name ^Mushu

modulation frequency number of harmonics

0.65 3

>> aquarium(2).amplitude

>> aquarium.amplitude

Help and Documentation

search browse

help doc

docsearch

Row, Column Indexing

>> gasprices(1,2) >> gasprices(3,6) >> gasprices(2,end)

>> gasprices(end,2) >> gasprices(end,end)

Multiple Row, Column Indices

>> Year = gasprices(:,1) >> gasprices([3,4],6:9)

>> gp08 = gasprices(end,2:end)

Indexed Assignment

>> x = gasprices(1,2)

reference

>> x = 1.96;

>> gasprices(1,2) = x

assignment

Concatenation

>> A A =

1 2 3 4 5 6 7 8 9

>> C = [A,B]

C =

1 2 3 1 0 0 4 5 6 0 1 0 7 8 9 0 0 1

>> B B =

1 0 0 0 1 0 0 0 1

>> D = [A;B]

D =

1 2 3 4 5 6 7 8 9 1 0 0 0 1 0 0 0 1

[]

Test Your Knowledge

1. (Select all that apply) Which of the following will create a matrix with three rows?

A. A = [zeros(2,4);ones(1,4)];

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

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

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

D. A = rand(3);

2. Given a 5-by-5 matrix A, A(4:end,3:4) will produce a matrix of what size?

A. 1-by-2 B. 2-by-2 C. 2-by-3 D. 3-by-2

Course Outline

● Working with the MATLAB User Interface

● Variables and Expressions

● Automating Commands with Scripts

● Automating Commands with Scripts

● Working with Data Files

Outline

• A modeling example

• The Command History

• Creating script files

• Creating script files

• Running scripts

• Code sections

• Publishing scripts

Course Example: Modeling a Whal Call

Sum of harmonics of a fundamental frequency Amplitude modulated: y(t) ₌ A(t)y₀(t)

= ∑

n

t nf t

y

( ) sin( 2 π

)

e

) 2

sin(

)

(t A₀e f t

A = ^−Bt π _m

Decaying oscillation

The Command History

The MATLAB Editor

% CALLMODEL Models a blue whale B call.

%

% Uses a model of the form y = A.*y0

% where A = A0*exp(-B*t).*sin(2*pi*fm*t)

% and y0 is a sum of harmonics

% yn = sin(2*pi*n*f0*t)

% Create the time base for the signal.

Script Files

H1 line

Help

% Create the time base for the signal.

fs = 4000;

t = 0:(1/fs):1.5;

% Set the fundamental frequency of the call.

f0 = 175;

% Create the harmonics.

y0 = sin(2*pi*f0*t) + sin(2*pi*2*f0*t) + sin(2*pi*3*f0*t);

Comments Code

callmodel.m

Running a Script

Code Sections

Create the time base for the signal

Set the fundamental frequency of the call

Create the

%%

%%

Create the harmonics

Create the envelope

Create the call

Plot the model call and listen to it

Publishing Code

Word^®

PDF

Test Your Knowledge

1. T/F: Anything following a % sign is ignored by MATLAB as a comment.

2. T/F: With code sections, you can modify your code and rerun it without having to save the file.

it without having to save the file.

3. T/F: MATLAB uses all the comment lines up to the first line of code as help for your script file.

4. T/F: Script files can access and modify any variables already in the base MATLAB workspace.

Course Outline

● Working with the MATLAB User Interface

● Variables and Expressions

● Automating Commands with Scripts

● Automating Commands with Scripts

● Working with Data Files

Outline

• File types and file formats

• Fixed-structure files

• Spreadsheets and

• Spreadsheets and delimited text files

• Low-level file I/O

File Types and File Formats

Audio Video Image

Scientific data

File Type File Format

BMP GIF JPEG PNG

Predefined structure

Scientific data Geographic data

…

Spreadsheet Delimited text

PNG

…

XLS CSV TXT

Flexible structure

???

Reading and Writing Fixed-Structure Files

audioread cdfread csvread dlmread

data = xyzread('file.xyz')

h5read imread ncread urlread xmlread ...

xyzwrite(data,'file.xyz')

Interactively Importing Text Files

and Spreadsheets

Exporting Spreadsheets

xlswrite

csvwrite csvwrite

dlmwrite

Read and Write data from EXCEL

XLSREAD

– num = xlsread('filename')

– num = xlsread('filename', -1)

– num = xlsread('filename', 'sheet') – num = xlsread('filename', 'range') – [num, txt] = xlsread('filename',

'sheet', 'range')

XLSWRITE

– xlswrite('filename', M)

– xlswrite('filename', M, 'sheet') – xlswrite('filename', M, 'range') – xlswrite('filename', M, 'sheet',

'range')

Test Your Knowledge

1. (Select all that apply) Which of the following can you change when importing a delimited text file with the Import Tool?

A. Which columns to import.

B. The format (text, number, date, etc.) of each column.

C. The delimiter character.

C. The delimiter character.

D. How to import missing values.

2. Suppose “ABC” is a supported format in MATLAB. Which command would import data from an ABC file mydata.abc into a matrix A?

A. mydata = abcread(A);

B. abcread(A,mydata);

C. abcread('mydata.abc',A);

D. A = abcread('mydata.abc');

E. A = abcread(mydata);