matlab course1

8/2/2019 Matlab Course1

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MATLAB - Introduction course

Fanilo RAMASOMANANA

Introduction course

MATLAB

[email protected]


Context

What is MATLAB?

Objectives

Introduction to Chapter 1:

Starting and Quitting MATLAB

MATLAB Desktop

Desktop Tools


What is MATLAB?

MATLAB is a commercial software of interactive calculus. It makes it

possible to carry out numerical simulations based on algorithms of

numerical analysis. It can thus be used for solving numericalproblems for the approximate resolution of differential equations,

partial differential equations, linear and nonlinear systems, or

scientific and engineering graphics, etc and to write programs in a

lower level language.

MATLAB provides a block diagram tool for modeling and simulating

dynamical systems, including signal processing, controls,

communications, and other complex systems ranging from

engineering and mathematics to chemistry, biology, and economics.


Objectives

The objective of this MATLAB's course is double:

the knowledge of this software is essential because it is more

and more used for calculus in industries and banks,

the knowledge of algorithms existing in the software and to

test new algorithms.


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Introduction

This chapter provides a brief introduction to starting and

quitting MATLAB, and the tools and functions that help you to

work with MATLAB variables and files.

Chapter 1:


Starting and Quitting MATLAB

On a Microsoft Windows platform, to start MATLAB, double-

click the MATLAB shortcut icon on your Windows desktop.

Starting MATLAB:

Quitting MATLAB:

To end your MATLAB session, select Exit MATLAB from theFile menu in the desktop, or type quit in the Command

Window.


MATLAB Desktop

When you start MATLAB, the MATLAB desktop appears,containing tools for managing files, variables, and applications

associated with MATLAB.

The first time MATLAB starts, the desktop appears as shown

in the following illustration.


MATLAB Desktop

You can change the

way your desktop looks

by opening, closing,

moving, and resizing

the tools in it. You can

also move tools

outside of the desktop

or return them back

inside the desktop.


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Desktop Tools

This section provides an introduction to MATLABs desktop

tools. The tools are:

Command Window

Command History

Help Browser

Current Directory

Workspace

Array Editor

Create M-Files


Desktop Tools

Use the Command

Window to make

calculations and run

functions which exist

in MATLAB and M-

files (programs)

created by us.

Command Window:


Desktop tools

Lines you enter in theCommand Window

are logged in the

Command History

window. In the

Command History,

you can view

previously used

functions, and copyand execute selected

lines.

Command History:


Desktop tools

Use the Help browser to search and view documentation for all

MathWorks products. The Help browser is a Web browser

integrated into the MATLAB desktop that displays HTML

documents.

To open the Help browser, click the help button in the toolbar, or

type helpbrowser in the Command Window.

Help Browser:


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Desktop tools

Help Browser:


Desktop tools

Current Directory Browser:

MATLAB file operations

use the current directory as

reference points. Any file

you want to run must be in

the current directory.

To search for, view, open,

and make changes toMATLAB-related directories

and files, use the MATLAB

Current Directory browser.


Desktop tools

Workspace Browser:

The MATLAB workspaceconsists of the set of variables

(named arrays) built up during

a MATLAB session and stored

in memory. You add variables

to the workspace by using

functions, running M-files, and

loading saved workspaces.

To view the workspace and

information about eachvariable, use the Workspace

browser.


Desktop tools

Workspace Browser:

To delete variables from the workspace, select the variable and selectDelete from the Edit menu. Alternatively, use the clear all function. The

workspace is not maintained after you end the MATLAB session.

To save the workspace to a file that can be read during a later MATLAB

session, select Save Workspace As from the File menu, or use the

save function. This saves the workspace to a file called a MAT-file,

which has a .mat extension.

To read in a MAT-file, select Import Data from the File menu, or usethe load function.


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Desktop tools

Workspace Browser (Array Editor):

Double-click on a

variable in the

Workspace browser

to see it in the Array

Editor.


Desktop tools

Create M-Files:

To create M-files, select New M-files from the File menu,

which allow to write programs and run MATLAB functions.

We can save the new algorithms in a any directory in a file

called a M-file, which has a .m extension.

If you just need to view the contents of an M-file, you can

display it in the Command Window by using the name of

the function or running this function.


Chapter 2

Operators fornumbers

Special functions for numbers

Operators for vectors

Special functions for vectors

Operators for matrices

Special functions for matrices


Expressions for numbers

+ Addition

- Subtraction

* Multiplication

pi 3.1415

i Imaginary unit

Inf Infinity

NaN Not a numberabs Absolute value

Operators for numbers:

Special functions:

sqrt Square root

log Logarithm

exp Exponentiel

sign Signe of the number(=1 if positif and 0 if negatif)

/ Division^ Power


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Special functions

sin Sine in radians

sind Sine in degrees

asin Inverse of the function Sine in radians

asind Inverse of the function Sine in degrees

cos Cosine in radians

cosd Cosine in degrees

acos Inverse of the function Cosine in radians

acosd Inverse of the function Cosine in degreestan Tangent in radians

cot Cotangent in radians

Trigonometric functions:


Complex numbers

abs the magnitude of the complex number

angle the phase angle of the complex number

real the real part of the complex number

imag the imaginary part of the complex number

conj the conjugate of the complex number

special functions:


Vectors

V=[2,3,7] is a row vectorV=[2;3;7] is a column vector

V change the vector from line to column or from

column to line.

Create a vector:

Operators for vectors:

+ Addition

- Subtraction

* Scalar product.* Element by element multiplication

./ Element by element division


Vectors

X=1:10 is a row vector containing the integers from 1 to

10. By default the increment here is equal to 1.

For a nonunit spacing, we can specify an increment. For

example:

X=100:-7:50 or X=0:pi/4:pi

Colon operator (:)


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Vectors

Special functionsones(1,3) is a row vector all components is equal to 1.

ones(3,1) is a column vector all components is equal to 1.

zeros(1,3) is a row vector all components is equal to 0.

zeros(3,1) is a column vector all components is equal to 0.

rand(1,3) is a row vector with random components between

0 and 1.

sum(X) computes the sum of the elements of X.

find(X


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Matrices

Special functions

diag(A) computes the diagonal of A.

det(A) computes the determinant of A.

inv(A) computes the inverse of A.

eig(A) computes the eigenvalues of A.

poly(A) computes the coefficients of the characteristicpolynomial of A.


Graphics

Plot of the function Sine

x=0:pi/100:2*pi;

y=sin(x);

plot(x,y)

We can label the axes and add a title:

xlabel(x)ylabel(Sine of x)

title(Plot of the Sine function)


Graphics

Multiple data sets in one graph

x=0:pi/100:2*pi;

y1=sin(x); y2=sin(x-0.25); y3=sin(x-0.5);

plot(x,y1,x,y2,x,y3)

The legend command provides an easy way to identify the

individual plots:

legend(sin(x),sin(x-0.25),sin(x-0.5))


Graphics

Multiple data sets in one graph

We can also use this format:figure(1);

plot(x,y1);

hold on;

plot(x,y2);

hold on;

plot(x,y3);

legend(sin(x),sin(x-0.25),sin(x-0.5))hold off;


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Graphics

Controlling the axes

By default, MATLAB finds the maxima and the minima of

the data to choose the axis limits. The axis command

enables you to specify your own limits:

axis([xmin xmax ymin ymax])

Or for three-dimensional graph:

axis([xmin xmax ymin ymax zmin zmax])


Graphics

Multiple plots in one figure

The subplot command enables you to display multiple plots

in the same window or print them on the same piece of

paper. Typing: subplot(m,n,p)

partitions the figure window into an m-by-n matrix of small

subplots and selects the pth subplot for the current plot.

The plots are numbered along first the top row of the figurewindow, then the second row, and so on.


Graphics

Multiple plots in one figureExample:

subplot(2,2,1)plot(x,y1);

hold off;

subplot(2,2,2)

plot(x,y2);

hold off;

Subplot(2,2,3)

Plot(x,y3);

hold off;

subplot(2,2,4);plot(x,y4);

hold off;


Graphics

Saving a figure

To save a figure, select save from the file menu or click on

the save button of the figure.

The figure is then saved as a fig file.


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Chapter 3

Programming with MATLAB

if statements

for loops

while loops


Chapter 3

if

The if statement evaluates a logical expression and

executes a group of statements when the expression is

true. The optional elseif and else keywords provide for the

execution of alternate groups of statements.

An end keyword, which matches the if, terminates the last

group of statements. The groups of statements aredelineated by the four keywords no braces or brackets

are involved.


Chapter 3

if (example):

if a < 0

a = a+1;

elseif a == 0

a=0;

else

a=a;

end


Chapter 3

for

The for loop repeats a group of statements a fixed,predetermined number of times.

A matching end delineates the loop.


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Chapter 3

for (example):

for i = 1:10

a(i) = i;

end


Chapter 3

while

The while loop repeats a group of statements an indefinite

number of times under control of a logical conditions.

A matching end delineates the loop.


Chapter 3

while (example):

while i < 0

a = i +1;

end


Chapter 3

The logical operators in the tests:

Logical operator MATLAB Symboland &

or |

equal ==

not equal ~=

Less than

Less or equal to =

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