Lab Session 2

Calculus

Lab session 2

Start

Victor Adsuar, Isaac Cicuendez , Guillermo Gandía and Ignacio Pérez.

Index

Introduction

Scripts

For

Functions

Fprintf and disp

If

While

1. Introduction

MATLAB as a programming language.

.m files

• - Scripts

• - Functions

(Non-Dependant of input arguments)

(Dependant of input arguments)

.m files

Warning: Function exp has the same name as a MATLAB built-in. We suggest you rename the function to avoid a potential name conflict.

Things to consider

• - The .m files must be stored in the current folder.
• - The name of a file must be different from the MATLAB reserved names.
• - The name must start with a letter.
• - Matlab is case-sensitive.

Creating a folder

You have to create a folder where your Matlab files will be stored. For example, you can make C:\matlabfiles

2. Scripts

A file that contains multiple sequential lines of MATLAB commands.

Make a new file inside your folder.

Now, in the live script editor, this script can be accessed by tiping its name.

3. For

Used for repeating calculations.

Where 1:n is a range and i is the variable.

The statement For is used when you know the number of iterations you want. While is more proper when you want the number of iterations to be determined inside the loop.

For example

In this case, we are using for in order to calculate the sum of the first ten natural numbers.

For example

Script exercises

Create two script files for computing the following expressions with an appropiate number of digits (vpa).

a)

b)

For example

Solutions:

a)

b)

For example

Script exercises

Repeat the last exercise with these expressions. Also, compare the result with log(2).

c)

d)

For example

Solutions:

c)

For example

Solutions:

d)

4. Functions

How do you do functions in MatLab?

Example: Create a function that calculates the product and the sum of three variables

Function Files

Syntax

Name of the function (Must be the same as the file name)

Variables that take the result value(output) -Always on []

Variables introduced/inputed to the funcion -Always on ()

Body of the function where you can operate with the variables

• The function starts with "function..." and ends with an "end"
• All arguments end with ;
• The file must be in the the mlx folder

Function Files

Syntax

Example

Name of the function (Must be the same as the file name)

Variables that take the result value(output) -Always on []

Variables introduced/inputed to the funcion -Always on ()

Body of the function where you can operate with the variables

Mlx file syntax

explanation

We asign a value for the input variables

On this output variable will be expresed our result

Result

With this code we asigned a number to our variables on the function we created before and it's result is: x=2 y=-6

Exsercises

Function exercises

For a given n that will be the input obtain one output is the sum when n=10, n=100 and 100000

For a given n that will be the input obtain one output is the sum when n=10, n=100 and 100000

Exsercises solved

Function exercises solved

For a given n that will be the input obtain one output is the sum when n=10, n=100 and 100000

For a given n that will be the input obtain one output is the sum when n=10, n=100 and 100000

5. Some usefulcommands

Me trying to understand matlab

FPRINTF

DISP

Fprintf

Disp

simple function used to show an string value or a function

fprintf: used to show text on the screen to the user

used for its quicknes

allows formating

does not allow formating

used for more complex outputs with various variables

It does an automatic line break

Syntax

text we want to display

while using display, we can only show the variable without text.

As previously mentioned, we can show variables and text with fprintf

if anyone is curious

we can achieve the same as with a fprintf , if we use the function num2str

EX 7

main code

function /m file

what the user sees

6. If , elseif, esle

If (condition)<statement> elseif (condition) <statement> else <statement> end

These are control statements to control the program.

IIf is used when you want your program to do a specefic thing if a condition is completed.After an if, it is posible to add more conditions with elseif and finally else is runned if none of the previous conditions is true.

7. While

What is it and how to use it

While is a tool in Matlab and other programming languages that allow us to repeat a process until a condition is completed.

E xample

Syntax

Let's try this program with B = 10 and B = 20

While (logical expresion)

Yes

Orders to execute

(Is the logical expresion true?)

No

End

We are going to the Moon

With a piece of paper (and "while")

We can obtain any distance by folding a piece of paper several times.

MATERIALS

Goals

To make a function to which a distance is introduce and it gives us the number of times that we have to fold a piece of paper in order to reach that distance.

Matlab

program

Function

While

Fold a paper from Albacete to Madrid

Paper

Fold a paper from the Earth to the Moon

END

Thanks for listening

Asking the user the distance in km

Paper initial thickness

((km -> mm)

function to calculate the folds

While

Calling the function