Basics of Programming using MATLAB Video Lecture - MATLAB Programming

hello and welcome to module 1 of introduction
to matlab programming course
ah in this module we are primarily going to
go over ah basics of matlab and uh introduction
to matlab programming, how the matlab ah is
laid out and so on okay
so this is the first lecture in this module
we will cover this module in approximately
5 lectures
the first lecture is on matlab basics
now this module overall is going to cover
ah after matlab basics, we are going to cover
arrays so thats the main ah aspect of working
in matlab basically arrays and ah matrices
so thats the 2nd lecture in this particular
module that we are going to cover
there after we are going to look at loops
and how to use loops for loops and while loops
in order to do ah various ah computations
ah that will be followed by ah talking about
matlab files matlab scripts and functions
and ah ah how to use matlab files which ah
will require a lot in the rest of the course
and finally will talk about plotting and ah
outputs in using matlab okay
alright so we will go over how to start a
matlab session, the layout of the matlab window
matlab editor and so on and so far
ah all of these is also available on matlabs
website the link for which is given right
over here so you can also in addition to this
video lecture ah i encourage you to also go
to matlab website and look at ah the video
and getting started with matlab
and that is what we are going to cover in
this particular lecture
ah so lets go and open ah the matlab
so i have just created a shortcut over here
for matlab in your case you may have to open
it using programme files
okay so this is how my matlab window looks
like ah when I open matlab ah your matlab
window may look slightly different and ah
however the main components of the window
will still remain the same
so this window has several components the
first is or the most important 1 is what is
known as the command window
ah so thats lot of times people just display
command window and nothing else thats also
fine
i like to display my current folder as well
as the workspace workspace is nothing but
the variables that you currently have in the
system defined in the system
okay you can move all these things around
by just clicking and dragging and as you can
see you can drag it
at various location so if you drag it and
put it on the current folder itself
ah you will basically have the 2 current folders
and workspace as 2 tabs
okay
and again you can drag this workspace back
over here and you can place it next to the
command window and then we can have current
folder workspace command window and so on
again as i said i like to place the workspace
variables and my current folder ah next to
each other or below each other to the left
hand side and thats what will we will do ah
again you can resize all these windows as
you find fit okay
ah so lets now this is the overall layout
of any matlab ah window that you might have
what we will do go and do is will start a
matlab editor as well in order to do that
you give a command edit space followed by
the file name so you will call this my first
file and i press enter
and we will be able to open my first file
and this is a blank file in matlab ah editor
this is where you can put in all your commands
all your ah functions and ah and expressions
assignments
so on and you can use matlab
so thats what ah i just wanted to give an
introduction to matlab ah now lets look
at the various matlab files that i have already
created in my folder
so currently in my folder i have 3 matlab
files ah ball animation ball trajectory and
ball trajectory fun that is ball trajectory
function if i go to matlab window i cannot
see these 3 files and thats because i am in
a different directory okay
so i can change my directory using the cd
command change directory command or i can
go and ah because i have ah used this particular
ah been to this particular directory before
i can look at that in my history
so i will just select it from the his history
and now i am able to see all all these files
okay
so let me just go and open ball trajectory
file by double clicking it and this is how
my file looks like i will go over ah the various
basics of this particular file in the power
point again
okay
okay ah this particular file uses the following
example ah this is an example of ah ah the
famous cricketer ah current captain of indian
team mahendra singh dhoni ah trying to hit
a ball for a six ah dhoni hits ball with an
initial velocity of 35 metres per second at
an angle of 45 degrees
and the question that we are asking ourselves
i have which will solved in matlab is whether
the ball is able to cross the boundary rope
that is ah 75 metres from ah where dhoni is
standing ah in order for this to be registered
as a 6
so we want to find out whether the ball lands
before 75 metres or after the 75 metre line
and we are going to solve this particular
problem using the simple equations that we
know of
and those equations are shown over here ah
the distance ah dx by dt depends on the horizontal
velocity dy by dt depends on the vertical
velocity ah the acceleration in the horizontal
direction is the 1 by the air drag and that
in the vertical direction is the 1 by ah the
gravitational force okay
so these are the equations that we have okay
and when we put this in matlab and we plot
we are going to get a plot of this nature
ah this is how the ball the ball trajectory
looks like at the end of every second ah or
at the end of every 0.1 seconds i am sorry
ah and the ball lands approximately 80 metres
from where dhoni is standing
so _______ and the matlab code that i had
quickly shown you earlier ah we will go over
that in a minute
and i will show
how this matlab code runs
in order to run this matlab code what we need
to do is type the file name ball trajectory
over here and press enter and this is going
to run and what i have done is also done as
small animation of how the ball moves and
lands at approximately 81 metres okay
once we have run this file this is what we
are able to see ah in the workspace all the
workspace variables we are now able to see
over here and what we see ah over here is
that the function has exited and we have come
back to the command prompt okay
lets go back to what the matlab code looks
like and this is how the matlab code looks
like the grin green things that you see over
here are basically the commands that we have
entered in matlab and i am going to go over
the various parts of the matlab
the over overall structure of this code looks
something like this we first have this input
block where we are defining parameters and
initial conditions we have the computation
block where we are setting up the ordinary
differential equations and solving them
and finally we have the output output block
where we are displaying the results and where
we are showing the animation
the animation is not going to be covered in
this particular course we are going to cover
rest of this stuff in this course we will
go over the things in the input block computation
block and output block the main parts of it
so what are the main parts main parts ah been
highlighted over here the first 1 is a comment
a comment starts with a percentage sign and
its coloured green in matlab editor window
so the comment that starts with 2 percentage
signs are basically they mark ah start and
end of a section in matlab
this is nothing but ah sectioning just to
identify for humans matlab ignores this particular
command its just for us to identify ah the
code or structure the code in a better way
the next thing is that we see over here is
an assignment assignment is basically you
have a variable and ah a constant is been
assigned to that variable instead of a constant
we can assign any expression to the variable
also
this is a mathematical expression 35 multiplied
by cos pi by 4 that is the mathematical expression
over here we will go over what variable ah
declarations and mathematical expressions
are in this particular module in lecture 1.2
ah over here what we see is a function this
function is a plot function and we are calling
this function with certain set of arguments
again i am not going to go over this ah in
this particular lecture we will go over that
later on in this module
ah in this particular ah example we have called
the function and we are not worried about
the outputs of that functions so we are just
calling this function as is if you want to
capture the outputs of this function we are
going to call the function and capture the
output as shown over here
again these are things that we will go over
the matlab basics and introduction to matlab
in this particular module ah in the subseq
subsequent lectures
okay so this again was the overall matlab
code we are going to ah uh cover various things
that are involved in coding of this matlab
in this particular course
okay so now let us go over what the basic
datatypes of matlab are now the 2 main datatypes
in matlab are going to be scalars and matrices
or arrays or vectors ah so when we talk about
scalars scalars are nothing but a single valued
ah variable where as arrays or matrices are
going to be ah of size m by n where m is the
number of rows and n is the number of columns
so we will go over some of these basic ah
things in this particular lecture and ah in
the subsequent lectures in this module
okay the most powerful thing about matlab
is that it works with matrices and that is
what mat in matlab stands for ah matlab ah
again we are going to look at how to assign
variables ah how to assign scalars how to
assign vectors how to assign arrays and matrices
and that is shown over here, a is the scalar
b is what is known as rom row vector c is
the matrix over here and d is what is known
as the column vector
so let us go and type these things in matlab
and see how that works
so lets say a equal to square bracket 1 comma
2 comma 5 if we type this close this square
bracket and press enter
we will now have a vect ah vector a this vector
a has ah 1 row and 3 columns over here and
that is shown ah as a row vector as seen over
here okay
if we type b equal to 1semi colon 2 semi colon
5 we are now instead going to get a column
vector so that has 3 rows and 1 single column
as shown over here
so the commas are going to separate various
ah elements in a particular row whereas semicolon
is going to separate ah ah various rows
so that way we can build a matrix as shown
over here 1 comma 2 that means thus this is
the first row 3 comma 5 thats the 2nd row
comma minus 1 comma 0 that becomes the 3rd
row so we have 3 rows and 2 columns in this
particular matrix
ah and this is what we can see over here so
and now let us say we wanted to define ah
a scalar so let us say q equal to 5 that becomes
a scalar okay as you can see over here every
time i type a command aahh the results of
the command get displayed ah in matlab window
i will just clear this matlab ah window so
if we dont want to display then we can basically
type sorry we can basically type this a
and we can end it with a semicolon so if a
line is ended with a semicolon ah then echo
is been suppressed as you can see the a ah
the variable gets assigned to the ah matrix
a however we do not see any result on the
screen
if you want to see the result on the screen
we can just type a press enter and we will
be able to see the result another thing we
can do is go to this workspace click on double
click on a and we will be able to see the
contents of this particular variable a okay
and ahh you can again close this particular
window so that ahh we can get back our command
window as before okay
so this is how to work with your matlab window
let us go over the basic mathematical expressions
so we want to look at mathematical ______
expressions that work with scalars as well
as mathematical vect expressions that are
going to work with vectors and matrices so
first we will go over the various scalar operations
so let us look at the scalar operations over
here the standard scalar operations plus minus
multiplication division and power thats carried
in addition to that logarithm and exponent
ahh are ah the in 1 shown in the second line
ah power square root sin cos tan asin acos
atan ah remainder round ceiling floor these
are the vario various ah scalar operations
and we have special variables that are shown
to the right hand side
so let us look at how these variable operations
works
so let us say we have 3 plus 4 and that is
7 so matlab has computed the value 7 and is
sign it has assign that value to a special
variable called a and s so if an expression
is calculated and you do not assign it to
any variable matlab automatically assigns
it to a special variable called a and s okay
let us now look at the matrix that we had
a so if we were to multiply a with a scalar
lets say 2 multiplied by a what is going to
happen is that each individual element of
a will get multiplied with ah by that particular
scalar we have over here
and this is going to be the result 2 4 and
10 as we expect the result to be
we had shown certain other ah commands that
was exp that is exponential so if we give
exp of a ah this is what we will get as you
can see this is ah exponent has ah acted upon
each and individual element of a so we get
ah exp or e to the power 1 e to the power
2 and e to the power 5 that because a was
1 2 5 and we get back
a row vector as seen in the result over here
okay if were to do exp of b note that b was
a column vector so if you were to do exp of
b we will get a column vector as a result
of this so we have this ah the result is going
to be ah column vector with 3 rows and 1 single
column and because we had not assigned it
to any variable the special variable a and
s gets assigned that particular value okay
so talking about special variables there are
certain other special variables for example
the value of pi if you type pi and press enter
we will get the value of pi likewise ah there
are other special variables also that we can
see ah in this
particular ah ah power point slide so eps
is machine precision i is the imaginary unit
that is ah square root of minus 1 inf is infinity
nan is not a number a and s we have already
seen before
and the other couple of
ah there is 1 more thing that you need to
know
so let us say if i assign the value pi equal
to 4 if i do that what is going to happen
is from this point onwards the standard value
of pi is going to be overridden by my expression
so next time when i calculate say pi by 4,
i am not going to get pi by 4 but i am going
to get 4 divided by 4 that is 1
that is because i have overridden the value
of pi by assigning the value over here if
you want to cancel this all i have to do do
is clear that variable by using the command
clear space pi and i am now able to recover
the value of the standard value of the pi
again that is 3 point 1416 okay
now if i want to clear all the variables in
the workspace i have to give the command clear
or i have to give the command clear all that
means everything in the workspace is going
to be cleared i give this command everything
in the workspace gets cleared as you can see
over here
and i can give the command clc to clean the
screen and my ah command prompt comes back
to the top with completely clean screen as
you can see over here okay
so let us go back to the basic mathematical
expressions we have seen the mathe mathematical
expressions for scalars and with that we will
come to the end of this particular lecture
okay as i said earlier 1 of the most powerful
features of matlab is that it is going to
be able work with matrices and arrays and
that is what we are going to cover in the
next lecture in this module that is lecture
1 point 2 okay
thank you and see you in the lecture 1 point
2