# 3.1 Variables in m-file environments

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This module provides a brief introduction to the use of variables in m-file environments.

## Variables

A variable is a named storage location that can be set to a particular value which can be used in subsequent computations. For example, we store a value of 5 in the variable a with the statement a=5 . This value remains in a until we store a different value (for example, using the command a=100 ) or we clear a using the command clear a . Once a variable is set to a particular value, we can get this value by using the variable name in an expression (e.g. a/2 ).

Suppose we wish to compute the circumference of a circle of diameter 5 units using the formula $c=d$ . We could first set the variable d to a value of 5: >>d = 5 d =5.000 Then we could compute the circumference and assign its value to the variable c : >>c = pi*d c =15.708 In this command, the product of the value of d (which is known because we earlier set it to 5) and the value of pi (which is a pre defined variable) is computed and the value of the product is stored in the variable c .

Variable names must begin with an upper- or lower-case letter. They may contain letters, digits, and underscores; they may not contain spaces or punctuation characters. Variable names are case sensitive, so A and a are different variables.

## Valid variable names

Which of the following are valid variable names?

• a
• B
• ecky_ecky_ecky_ecky_ptang_zoo_boing
• ecky ecky ecky ecky ptang zoo boing
• 2nd
• John-Bigboote

• Valid.
• Valid.
• Valid.
• Invalid, because the variable name contains spaces.
• Invalid, because the variable name begins with a number.
• Invalid, because the variable name contains a dash.

There are several predefined variables. The most commonly used include

• ans - the default variable in which computation results are stored.
• pi -.
• i or j - $\sqrt{-1}$ .
Once assigned, variable names remain until they are reassigned or eliminated by the clear command.

Variables can contain several types of numerical values. These types include the following:

• Scalar - a scalar is a single value (i.e. a number). c and d in are scalar variables.
• Vector - a vector is an ordered series of numbers.
• Matrices - a matrix is a rectangular array of numbers. The ability to do computations on vectors and matrices gives MATLAB its name (MATrix LABoratory).
• strings - variables may also contain strings of characters.

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
how did you get the value of 2000N.What calculations are needed to arrive at it
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