# 9.9 An introduction to matlab: editing files and creating functions

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This module is part of the collection, A First Course in Electrical and Computer Engineering . The LaTeX source files for this collection were created using an optical character recognition technology, and because of this process there may be more errors than usual. Please contact us if you discover any errors.

If you quit MATLAB now, all the commands you have typed will be lost. This is where the Edit window is useful. If you choose new from the File menu, a new window appears with the title Edit 1 : Untitled . In this window, you should type in all the commands you would like MATLAB to execute atonce. When you are finished typing, you may save the file by choosing save or save as in the file menu and by entering a name for the file. If the edit window is active (that is, if it appears in front), then choose save and go from the file menu to save the file and execute it. If the command window is active,then you can execute the file by entering its name.

Editing Files. To test your understanding of file editing, enter the following commands in a file named myfile:

You do not have to type the % sign and the text that follows it. These are simply comments in a file. They are ignored by the MATLAB interpreter.You should, however, make a habit of adding comments (preceded by %) to your file if you want to be able to understand programs that have been writtenlong ago.

Do not forget to save your file. Such a file is called a script file . It contains MATLAB commands that could have been entered one by one in thecommand window. You have three ways to execute a script file:

1. with the edit window active, choose save and go from the file menu;
2. with the command window active, enter the file name; or
3. with the command window active, choose run script ... from the M-file menu. In this case, a menu pops up to ask you which file you want to execute.

Try each of these three methods in order to get used to their differences. Figure 1 shows the plot that you should get.

Creating Functions. MATLAB puts many commands at your disposal, and you just have to enter their names (with or without arguments) to execute them. Some commands are built in to MATLAB, and others arecontained in files to which you have access (not to modify them, but to see how things are done). You can try to display the contents of a command filein the command window by entering the command type filename. Enter type plot. You should get the message

This means that the commandis a build-in function and thus cannot be typed by the user (it is compiled with the program). Similarly, try to typethe function file containing the commandby entering the command. You should get type sinh

This is a typical example of a function file . It differs from a script file by the fact that the first line contains the word. What it does is make the commandequivalent to the command. The variableis the input argument (there could be more than one), and y is the output argument (there also could be more than one). The second line contains comments about the function and its arguments. They can spreadto several lines. Display them by typing the command. The third line contains the actual function commands (there could also be several lines). help sinh

As an exercise, enter the function: perp(x)

Evaluateon various complex numbers. Replace the last line by;. Do you get the same result? Why? y = x*j

Note that local variables are just that– local . Only the input and out- put arguments are kept in memory after the function is called and executed.For more on functions and multiple arguments, see the MATLAB manual. In the previous example, the variable $j$ is local. If, before using the function, you use the same variable $j$ , its contents will not be affected by the command. Verify this. perp(z)

Normally, while a file (script or function) is executed, the commands are not displayed on the command window. Just the results are displayed.The commandallows you to view all the instructions. This is useful for debugging and demonstrations. It is turned off by typing. echo off

Is there any normative that regulates the use of silver nanoparticles?
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
why we need to study biomolecules, molecular biology in nanotechnology?
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
why?
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
what does nano mean?
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
it is a goid question and i want to know the answer as well
Maciej
Abigail
for teaching engĺish at school how nano technology help us
Anassong
Do somebody tell me a best nano engineering book for beginners?
there is no specific books for beginners but there is book called principle of nanotechnology
NANO
what is fullerene does it is used to make bukky balls
are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
so some one know about replacing silicon atom with phosphorous in semiconductors device?
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
for screen printed electrodes ?
SUYASH
What is lattice structure?
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
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