# 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.

Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
I only see partial conversation and what's the question here!
what about nanotechnology for water purification
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
what is the stm
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
what is Nano technology ?
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
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
hi
Loga
what does nano mean?
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
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