Fundamentals of matlab programming

MATLAB orientation courseMATLAB orientation course
Fundamentals ofFundamentals of
MATLAB ProgrammingMATLAB Programming
Delivered byDelivered by
Chirodeep BakliChirodeep Bakli
Research ScholarResearch Scholar
Indian Institute of Technology, KharagpurIndian Institute of Technology, Kharagpur

The m fileThe m file
 Write a series of MATLAB statements into aWrite a series of MATLAB statements into a
file and then execute them with a singlefile and then execute them with a single
command.command.
 Write your program in an ordinary text editorWrite your program in an ordinary text editor
(Notepad), giving the file a name of(Notepad), giving the file a name of
filename.m. The term you use for filenamefilename.m. The term you use for filename
becomes the new command that MATLABbecomes the new command that MATLAB
associates with the program. The fileassociates with the program. The file
extension of .m makes this a MATLAB M-file.extension of .m makes this a MATLAB M-file.

Script M-FilesScript M-Files Function M-FilesFunction M-Files
Do not accept inputDo not accept input
arguments or returnarguments or return
output argumentsoutput arguments
Can accept inputCan accept input
arguments and returnarguments and return
output argumentsoutput arguments
Operate on data in theOperate on data in the
workspaceworkspace
Internal variables areInternal variables are
local to the function bylocal to the function by
defaultdefault
Useful for automating aUseful for automating a
series of steps you needseries of steps you need
to perform many timesto perform many times
Useful for extending theUseful for extending the
MATLAB language forMATLAB language for
your applicationyour application
Kinds of M filesKinds of M files

An example of a script m-fileAn example of a script m-file
Factorial.mFactorial.m
n=10;n=10;
factorial=1;factorial=1;
forfor i=1:1:ni=1:1:n
factorial=factorial*i;factorial=factorial*i;
endend

An example of a function m-fileAn example of a function m-file
CommentComment
defines thedefines the
function name,function name,
and the numberand the number
and order ofand order of
input and outputinput and output
parametersparameters
H1 stands for "help 1" line.H1 stands for "help 1" line.
MATLAB displays the H1MATLAB displays the H1
line for a function when youline for a function when you
useuse lookforlookfor or request helpor request help
on an entire directory.on an entire directory.

Creating M-Files: Accessing Text EditorsCreating M-Files: Accessing Text Editors
>> edit fact>> edit fact.m.m

Listing filesListing files
>> what>> what (List the names of the files in your(List the names of the files in your
current directory)current directory)

Checking file contentChecking file content
>> type fact>> type fact (List the contents of M-file fact.m)(List the contents of M-file fact.m)

Calling functionCalling function
Call the fact functionCall the fact function
>> fact(5)>> fact(5)

Some m-File FunctionsSome m-File Functions
FunctionFunction DescriptionDescription
runrun
Run script that is not on currentRun script that is not on current
pathpath
type filenametype filename
lists the contents of the file given alists the contents of the file given a
full pathnamefull pathname
Edit funEdit fun opens the file fun.m in a text editoropens the file fun.m in a text editor
mfilenamemfilename Name of currently running M-fileName of currently running M-file
namelengthmaxnamelengthmax Return maximum identifier lengthReturn maximum identifier length
echoecho
Echoes the script file contents asEchoes the script file contents as
they are executedthey are executed

inputinput Request user inputRequest user input
Disp (variablename)Disp (variablename)
Displays results withoutDisplays results without
printing variable namesprinting variable names
beepbeep Makes computer beepMakes computer beep
evaleval
Interpret strings containingInterpret strings containing
MATLAB expressionsMATLAB expressions
fevalfeval Evaluate functionEvaluate function

pausepause
pause (n)pause (n)
Pauses and waits until user pressesPauses and waits until user presses
any keyboard key.any keyboard key.
Pause (n) pauses for n seconds andPause (n) pauses for n seconds and
then continuesthen continues
waitforbuttonpresswaitforbuttonpress
Pauses until user presses mousePauses until user presses mouse
button or any keyboard keybutton or any keyboard key
keyboardkeyboard
Temporarily gives control to keyboard.Temporarily gives control to keyboard.
The keyboard mode is terminated byThe keyboard mode is terminated by
executing the commandexecuting the command RETURNRETURN
DBQUITDBQUIT can also be used to get outcan also be used to get out
of keyboard mode but in this case theof keyboard mode but in this case the
invoking M-file is terminated.invoking M-file is terminated.

VariablesVariables
 The same guidelines that apply to MATLABThe same guidelines that apply to MATLAB
variables at the command line also apply tovariables at the command line also apply to
variables in M-files.variables in M-files.
 No need to type or declare variables used inNo need to type or declare variables used in
M-files, (with the possible exception ofM-files, (with the possible exception of
designating them asdesignating them as globalglobal oror persistentpersistent).).
 Before assigning one variable to another, youBefore assigning one variable to another, you
must be sure that the variable on the right-must be sure that the variable on the right-
hand side of the assignment has a value.hand side of the assignment has a value.

 Any operation that assigns a value to a variableAny operation that assigns a value to a variable
creates the variable, if needed, or overwrites itscreates the variable, if needed, or overwrites its
current value, if it already exists.current value, if it already exists.
 MATLAB variable names must begin with aMATLAB variable names must begin with a
letter, which may be followed by any combinationletter, which may be followed by any combination
of letters, digits, and underscores.of letters, digits, and underscores.
 MATLAB distinguishes between uppercase andMATLAB distinguishes between uppercase and
lowercase characters, so A and a are not thelowercase characters, so A and a are not the
same variable.same variable.
Avoid Using Function Names for VariablesAvoid Using Function Names for Variables
VariablesVariables

 Each MATLAB function has its own local variables.Each MATLAB function has its own local variables.
These are separate from those of other functions,These are separate from those of other functions,
and from those of the base workspace.and from those of the base workspace.
 Variables defined in a function do not remain inVariables defined in a function do not remain in
memory from one function call to the next, unlessmemory from one function call to the next, unless
they are defined asthey are defined as globalglobal oror persistentpersistent..
 Scripts, on the other hand, do not have a separateScripts, on the other hand, do not have a separate
workspace. They store their variables in aworkspace. They store their variables in a
workspace that is shared with the caller of theworkspace that is shared with the caller of the
script. When called from the command line, theyscript. When called from the command line, they
share the base workspace. When called from ashare the base workspace. When called from a
function, they share that function's workspace.function, they share that function's workspace.
Local VariablesLocal Variables

Global VariablesGlobal Variables
 If several functions all declare a particular name asIf several functions all declare a particular name as
globalglobal, then they all share a single copy of that, then they all share a single copy of that
variable.variable.
 Any assignment to that variable, in any function, isAny assignment to that variable, in any function, is
available to all the other functions declaring itavailable to all the other functions declaring it globalglobal..
 Creating Global VariablesCreating Global Variables
Each function that uses a global variable must firstEach function that uses a global variable must first
declare the variable as global.declare the variable as global.
You would declare global variable MAXLEN as follows:You would declare global variable MAXLEN as follows:
global MAXLENglobal MAXLEN
 To access the variable from the MATLAB commandTo access the variable from the MATLAB command
line, you must declare it as global at the commandline, you must declare it as global at the command
line.line.

function yp = myfunction(y)function yp = myfunction(y)
%The function you want to check.%The function you want to check.
global ALPHAglobal ALPHA
yp = [y-ALPHA*y];yp = [y-ALPHA*y];
 Suppose, for example, you want to study the effectSuppose, for example, you want to study the effect
coefficients on a equation. Create an M-file,coefficients on a equation. Create an M-file,
myfunction.m.myfunction.m.

Then in the commandThen in the command
prompt enter theprompt enter the
statementsstatements
global ALPHAglobal ALPHA
ALPHA = 0.01ALPHA = 0.01
y=myfunction(1:10);y=myfunction(1:10);
The global statement make the values assigned to ALPHA atThe global statement make the values assigned to ALPHA at
the command prompt available inside the function defined bythe command prompt available inside the function defined by
myfunction.m. They can be modified interactively and newmyfunction.m. They can be modified interactively and new
solutions obtained without editing any files.solutions obtained without editing any files.

Persistent VariablesPersistent Variables
Characteristics of persistent variables are:Characteristics of persistent variables are:
1.1. You can only use them in functions.You can only use them in functions.
2.2. Other functions are not allowed access to them.Other functions are not allowed access to them.
3.3. MATLAB does not clear them from memory whenMATLAB does not clear them from memory when
the function exits, so their value is retained fromthe function exits, so their value is retained from
one function call to the next.one function call to the next.
You must declare persistent variables as persistentYou must declare persistent variables as persistent
before you can use them in a function. It is usually bestbefore you can use them in a function. It is usually best
to put persistent declarations toward the beginning ofto put persistent declarations toward the beginning of
the function. You would declare persistent variable X asthe function. You would declare persistent variable X as
follows:follows:
>> persistent X>> persistent X

Special ValuesSpecial Values
 ans:ans: Most recent answer (variable). If you doMost recent answer (variable). If you do
not assign an output variable to annot assign an output variable to an
expression, MATLAB automatically storesexpression, MATLAB automatically stores
the result in ans.the result in ans.
 pi:pi: 3.1415926535897...3.1415926535897...
 eps:eps: Machine epsilonMachine epsilon
 inf:inf:Stands for infinityStands for infinity
 NaN:NaN: Stands for Not-a-NumberStands for Not-a-Number

OperatorsOperators
1.1. Arithmetic operatorsArithmetic operators - perform numeric- perform numeric
computationscomputations
2.2. Relational operatorsRelational operators - compare operands- compare operands
quantitativelyquantitatively
3.3. Logical operatorsLogical operators - use the logical- use the logical
operators AND, ORoperators AND, OR
The MATLAB operators fall into threeThe MATLAB operators fall into three
categories:categories:

Arithmetic OperatorsArithmetic Operators
OperatorOperator DescriptionDescription
++ AdditionAddition
-- SubtractionSubtraction
.*.* MultiplicationMultiplication
././ Right divisionRight division
.. Left divisionLeft division
++ Unary plusUnary plus

-- Unary minusUnary minus
:: Colon operatorColon operator
.^.^ PowerPower
.'.' TransposeTranspose
'' Complex conjugate transposeComplex conjugate transpose
** Matrix multiplicationMatrix multiplication
// Matrix right divisionMatrix right division
Matrix left divisionMatrix left division
^^ Matrix powerMatrix power

// Slash or matrix right division.Slash or matrix right division.
B/A is roughly the sameB/A is roughly the same
as B*inv(A). Moreas B*inv(A). More
precisely, B/A = (A'B')'.precisely, B/A = (A'B')'.
././ Array right division.Array right division.
A./B is the matrix withA./B is the matrix with
elements A(i,j)/B(i,j). Aelements A(i,j)/B(i,j). A
and B must have theand B must have the
same size, unless one ofsame size, unless one of
them is a scalar.them is a scalar.

Backslash or matrix leftBackslash or matrix left
division.division.
If A is a square matrix,If A is a square matrix,
AB is inv(A)*B.AB is inv(A)*B.
.. Array left division.Array left division.
A.B is the matrix withA.B is the matrix with
elements B(i,j)/A(i,j). Aelements B(i,j)/A(i,j). A
and B must have theand B must have the
same size, unless one ofsame size, unless one of
them is a scalar.them is a scalar.

<< Less thanLess than
<=<= Less than or equal toLess than or equal to
>> Greater thanGreater than
>=>= Greater than or equal toGreater than or equal to
==== Equal toEqual to
~=~= Not equal toNot equal to
Relational OperatorsRelational Operators

Logical OperatorsLogical Operators
MATLAB offers three types of logical operatorMATLAB offers three types of logical operator
and functions.and functions.
 Element-wiseElement-wise - operate on corresponding- operate on corresponding
elements of logical arrays.elements of logical arrays.
 Bit-wiseBit-wise - operate on corresponding bits- operate on corresponding bits
of integer values or arrays.of integer values or arrays.
 Short-circuitShort-circuit - operate on scalar, logical- operate on scalar, logical
expressions.expressions.

Element-Wise Operators and FunctionsElement-Wise Operators and Functions
 Perform element-wise logical operations onPerform element-wise logical operations on
their inputs to produce a like-sized outputtheir inputs to produce a like-sized output
array.array.

A and b must have equal dimensions, withA and b must have equal dimensions, with
each dimension being the same size.each dimension being the same size.
Element-Wise Operators and FunctionsElement-Wise Operators and Functions

Bit-Wise Operators and FunctionsBit-Wise Operators and Functions
Logically mask, invert, or shift the bits of an unsignedLogically mask, invert, or shift the bits of an unsigned
integer signalinteger signal
OperatioOperatio
nn
MaskMask
BitBit
InputInput
BitBit
OutputOutput
BitBit
ANDAND 11 11 11
11 00 00
00 11 00
00 00 00
OROR 11 11 11
00 11 11
11 00 11
00 00 00
XORXOR 11 11 00
11 00 11
00 11 11
00 00 00

 Perform AND and OR operations on logicalPerform AND and OR operations on logical
expressions containing scalar values.expressions containing scalar values.
 They are short-circuit operators in that they onlyThey are short-circuit operators in that they only
evaluate their second operand when the result is notevaluate their second operand when the result is not
fully determined by the first operand.fully determined by the first operand.
Short-Circuit OperatorsShort-Circuit Operators
&&&&
Returns true (1) if both inputs evaluate to true,Returns true (1) if both inputs evaluate to true,
and false (0) if they do not.and false (0) if they do not.
||||
Returns true (1) if either input, or both,Returns true (1) if either input, or both,
evaluate to true, and false (0) if they do not.evaluate to true, and false (0) if they do not.

Example:Example:
if ((A==10)&&(B==20))if ((A==10)&&(B==20))
……....
endend
if ((A==10)||(B==20))if ((A==10)||(B==20))
……....
endend
Short-Circuit OperatorsShort-Circuit Operators

Flow ControlFlow Control
 ifif,, elseelse andand elseifelseif, executes a group of, executes a group of
statements based on some logicalstatements based on some logical
condition.condition.
 switchswitch,, casecase andand otherwiseotherwise, executes, executes
different groups of statements dependingdifferent groups of statements depending
on the value of some logical condition.on the value of some logical condition.
 whilewhile executes a group of statements anexecutes a group of statements an
indefinite number of times, based on someindefinite number of times, based on some
logical condition.logical condition.

 forfor executes a group of statements a fixedexecutes a group of statements a fixed
number of times.number of times.
 continuecontinue passes control to the next iterationpasses control to the next iteration
of aof a forfor oror whilewhile loop, skipping anyloop, skipping any
remaining statements in the body of theremaining statements in the body of the
loop.loop.
 breakbreak terminates execution of aterminates execution of a forfor oror whilewhile
loop.loop.
 returnreturn causes execution to return to thecauses execution to return to the
invoking function.invoking function.
 All flow constructs useAll flow constructs use endend to indicate theto indicate the
end of the flow control block.end of the flow control block.
Flow ContrFlow Controlol

If-else-end ConstructionsIf-else-end Constructions
myfile.mmyfile.m

 Unlike the C languageUnlike the C language
switch construct, theswitch construct, the
MATLABMATLAB switch does notswitch does not
"fall through.""fall through." That is, if theThat is, if the
first case statement is true,first case statement is true,
other case statements doother case statements do
not execute. Therefore,not execute. Therefore,
breakbreak statements are notstatements are not
used.used.
 switch can handle multiple conditions in a single caseswitch can handle multiple conditions in a single case
statement by enclosing the case expression in a cell array.statement by enclosing the case expression in a cell array.
myfile.mmyfile.mSwitch-Case ConstructionsSwitch-Case Constructions

TheThe whilewhile loop executes a statement or group ofloop executes a statement or group of
statements repeatedly as long as the controllingstatements repeatedly as long as the controlling
expression is true (1).expression is true (1).
while expressionwhile expression
endend
Exit aExit a whilewhile loop at any time using theloop at any time using the breakbreak
statement.statement.
ExampleExample
Infinite loopInfinite loop
While LoopsWhile Loops

TheThe forfor loop executes a statement or group of statementsloop executes a statement or group of statements
a predetermined number of times.a predetermined number of times.
for index = indexstart:increment:indexendfor index = indexstart:increment:indexend
endend
default increment is 1default increment is 1.You can specify any increment,.You can specify any increment,
including aincluding a negativenegative one.one.
x=[1,2,3,8,4];x=[1,2,3,8,4];
for i = 2:6for i = 2:6
x(i) = 2*x(i-1);x(i) = 2*x(i-1);
endend
For LoopsFor Loops

You can nest multiple for loops.You can nest multiple for loops.
x=[1,2,3,8,4;4 9 7 10 15];x=[1,2,3,8,4;4 9 7 10 15];
m=length(x(:,1));m=length(x(:,1));
n=length(x(1,:));n=length(x(1,:));
for i = 1:mfor i = 1:m
for j = 1:nfor j = 1:n
A(i,j) = 1/(i + j - 1);A(i,j) = 1/(i + j - 1);
endend
endend
For LoopsFor Loops

Vectorizing LoopsVectorizing Loops
 MATLAB is designed for vector and matrix operations.MATLAB is designed for vector and matrix operations.
 You can often speed up your M-file code by using vectorizingYou can often speed up your M-file code by using vectorizing
algorithms that take advantage of this design.algorithms that take advantage of this design.
 Vectorization means converting for and while loops toVectorization means converting for and while loops to
equivalent vector or matrix operations.equivalent vector or matrix operations.
Compute the sine of 1001 values ranging from 0 to 10.Compute the sine of 1001 values ranging from 0 to 10.
AA vectorized versionvectorized version of the same codeof the same code
is:is:
tictic
t = 0:.001:10;t = 0:.001:10;
y = sin(t);y = sin(t);
toctoc
tictic
i = 0;i = 0;
for t = 0:.001:10for t = 0:.001:10
i = i+1;i = i+1;
y(i) = sin(t);y(i) = sin(t);
endend
toc;toc;

File HandlingFile Handling
The most commonly used, high-level, file I/OThe most commonly used, high-level, file I/O
functions in MATLAB arefunctions in MATLAB are savesave andand loadload..
savesave
 Saves workspace variables on disk.Saves workspace variables on disk.
As an alternative to the save function, selectAs an alternative to the save function, select
Save Workspace As from the File menu in theSave Workspace As from the File menu in the
MATLAB desktop, or use the WorkspaceMATLAB desktop, or use the Workspace
browser.browser.

SyntaxSyntax
• savesave
• save filenamesave filename
• save filename var1 var2 ...save filename var1 var2 ...
• save('filename', ...)save('filename', ...)
DescriptionDescription
• savesave by itself, stores all workspace variablesby itself, stores all workspace variables
in a binary format in the current directory inin a binary format in the current directory in
a file named matlab.mat. Retrieve the dataa file named matlab.mat. Retrieve the data
with load.with load.

LoadLoad
 Load workspace variables from diskLoad workspace variables from disk
SyntaxSyntax
•loadload
•load filenameload filename
•load filename X Y Zload filename X Y Z
DescriptionDescription
•loadload - loads all the variables from the MAT-file- loads all the variables from the MAT-file
matlab.mat, if it exists, and returns an error if it doesn'tmatlab.mat, if it exists, and returns an error if it doesn't
exist.exist.
•load filename X Y Zload filename X Y Z ... loads just the specified variables... loads just the specified variables
from the MAT-file. The wildcard '*' loads variables thatfrom the MAT-file. The wildcard '*' loads variables that
match a pattern (MAT-file only).match a pattern (MAT-file only).

Read an ASCII delimited file into a matrixRead an ASCII delimited file into a matrix
Graphical InterfaceGraphical Interface
As an alternative to dlmread, use the ImportAs an alternative to dlmread, use the Import
Wizard. To activate the Import Wizard, selectWizard. To activate the Import Wizard, select
Import data from the File menu.Import data from the File menu.
SyntaxSyntax
M = dlmread(filename,delimiter)M = dlmread(filename,delimiter)
M = dlmread(filename,delimiter,R,C)M = dlmread(filename,delimiter,R,C)
M = dlmread(filename,delimiter,range)M = dlmread(filename,delimiter,range)

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Fundamentals of matlab programming

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