Matlab Functions

Matlab Functions13033386-018 Umar Azeem

University of Gujrat

Introduction A function is a MATLAB program that can accept inputs and produce outputsA function is a group of statements that together perform a task. Functions can accept more than one input arguments and may return more than one output arguments

Why use functions?

Functions provide reusable code

Use same code in more than one place in program without rewriting code

Reuse code by calling in different programs

Basic types of function

Built in FunctionUser define Function

Built in Function

Operators and Special Characters+ Plus; addition operator.- Minus; subtraction operator.* Scalar and matrix multiplication operator..* Array multiplication operator.^ Scalar and matrix exponentiation operator..^ Array exponentiation operator.\ Left-division operator./ Right-division operator..\ Array left-division operator../ Array right-division operator.

Operators and Special Characters : Colon; generates regularly spaced elements and represents an entire row or column.( ) Parentheses; encloses function arguments and array indices; overrides precedence.[ ] Brackets; enclosures array elements.., Comma; separates statements and elements in a row.; Semicolon; separates columns and suppresses display.% Percent sign; designates a comment and specifies formatting.= Assignment (replacement) operator.

Commands for Managing a Sessionclc -Clears Command window.Clear- Removes variables from memory.exist -Checks for existence of file or variable.Global- Declares variables to be global.help -Searches for a help topic.Lookfor- Searches help entries for a keyword.quit -Stops MATLAB.who -Lists current variables.whos -Lists current variables (long display).

System and File CommandsCd-Changes current directory.Date-Displays current date.Delete-Deletes a file.Diary-Switches on/off diary file recording.dir-Lists all files in current directory.Load-Loads workspace variables from a file.Path-Displays search path.Save-Saves workspace variables in a file.

Data Analysismax(x)min(x)mean(x)median(x)sum(x)

Trigonometric Functionssin(x)sinecos(x)cosinetan(x)tangentasin(x)inverse sinesinh(x)hyperbolic sineasinh(x)inverse hyperbolic sinesind(x)sine with degree inputasind(x)inverse sin with degree output

User define Function

Before you start

Identify the functionDecide the function nameDecide the input variablesDecide the output variablesFile name must be the function name.

Function Syntaxfunction[a, b, c]= basicmath(x,y)%BASICMATH Basic Mathematical function% basicmath(x,y) is a sample matlab function to perform% basic mathematical operations on input variables x & y% outputs of the function are sum, difference and product of input arguments.

a = x + y;b = x y;c = x * y;14Output argumentsExecutable code

Comments about the functionName of the function

Input argumentsdeclaration statement

Syntax The declaration statement function is used to define the file as a function.It must be typed in lower case letters.Input argumentsCan be zero or more input arguments.Output argumentsTypes inside the square brackets [ ]Give a meaningful variable name.

Function with one OutputThe function have only one out put you dont need to put it inside the square brackets [ ]

Example:The function in a file namedaverage.mthat accepts an input vector, calculates the average of the values, and returns a single result.function y = average(x) y = sum(x)/length(x); end

Functions with more OutputsWhen there are more than one output arguments put them in a square bracket.Example

function[a, b, c]= basicmath(x,y)a = x + y;b = x y;c = x * y;

Calling a user-defined functionA function can be called from the command window or inside a script or function.To run a function in command window, just type the name of comment with proper input and output argumentsFor example consider the function basicmath>> [a,b,c] = basicmath (2,3)a = 5b = -1c = 6

Points to RememberFunction name and file name must be same.Unlike other programming languages, Function in MATLAB can return more than one value.Syntax: function outputs=function_name(inputs) There is no starting and ending curly braceS to enclose the body of function, instead, there is an end statement which signifies end of function.

Points to Remember

To run a function we type a function name with valid arguments in command window area.If function returns two or more ouputs,to see all the outputs, we must not put semicolon after the output statement. Note: if we put semicolon, we will see only the first output.

SummaryMATLAB contains a wide array of predefined functionsElementary Math FunctionsTrigonometric FunctionsData Analysis FunctionsRandom NumbersComplex Numbers

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