WEBVTT
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YOSSI FARJOUN: This is
Dr. MATLAB, Lecture 1--
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Using MATLAB for the First Time.
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When you turn MATLAB
on for the first time,
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you'll be greeted with a
window that looks like this.
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The first thing we do
is close all the windows
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that we don't need initially--
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Current Directory, Workspace,
and Command History.
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We're left with
a command window.
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This is the command prompt.
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And this is the flashing cursor
where our input will be placed.
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The first thing we
want to do is try using
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MATLAB as a giant calculator.
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So for example, we can ask
MATLAB to calculate 1 plus 1.
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The answer is 2.
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So we type what
we want, 3 plus 4.
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Hit Enter and we
get the answer--
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3 times 4, 1 plus 2 times
3, 2 to the power of 4,
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5 to the power of 3, et cetera.
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We can also ask whether
two numbers are the same,
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or whether one is
greater than the other.
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So to see if 4 is greater
than 5, we type this.
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This will tell us
that the answer
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is no, 4 is not greater than 5.
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We can ask is 4 less than 5.
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The answer is yes,
4 is less than 5.
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Sometimes we need a function
and expression, not just
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an operator.
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So for example, to
find the remainder,
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we need to use the function rem.
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Here is the remainder of
15 when divided by 4--
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rem(15,4).
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The answer is 3.
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To find out more
about a function,
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we use the help command.
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help rem will tell us everything
we need to know about rem--
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the remainder after division.
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There's a bit of an
explanation, some conventions.
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And the "see also"--
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this is perhaps one of the most
important parts of the help
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file-- is to help you
find other commands that
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are useful and related
to this command.
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I encourage you to try to find
the difference between mod
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and rem.
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Other than calculating
expressions,
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we can also assign their
value into variables.
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So for example, if I want to
create a variable named x,
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I type x equals and then
the value that I want.
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So for example, x=1 will create
a variable called x and put 1
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as the value into it.
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I can also put the result of
an expression into a variable.
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Here's y=2*3.
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Of course, that's 6.
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So it calculates the 6 and
puts 2 times 3 into it.
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So now y is 6 and x is 1.
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And I can use x and y if
they are numbers. x+y,
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the answer is 7.
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If I try to use a variable
that doesn't yet exist,
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for example z+y,
I get an error--
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undefined function or variables.
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Sometimes, you're
looking for a command
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but you don't know the command.
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You know that you're
looking for something,
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bu you just don't know
what it's called in MATLAB.
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In that case, you
should be using lookfor
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to find the command
you're looking for.
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So for example, lookfor
square will give you
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all the commands that have the
word square in their help file.
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Of course, I was looking for,
in this case, square root.
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And here it is.
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I can either click
on this and that
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will give me the help
file of the square root.
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Or I can just type help sqrt.
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And that will give the same.
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Square root finds the
square of the elements.
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So if I do sqrt(4), I get 2.
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Notice that I get
complex results
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if I get a non-positive input.
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So sqrt(-3) is the square root
of three times i, which is,
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of course, very nice to know.
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So 2i^2 should give me -4, and
indeed, 2i squared gives me -4.
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On the command line,
there is a useful trick
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involving the "up" button.
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Sometimes, you're
looking for something
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or you're typing something and
you make a typo, like this.
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I've swapped the
L and the E. Now
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I could retype
everything from scratch,
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or I can press the up key--
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up arrow-- and then the left
arrow until I can delete the E,
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and put it in the right place.
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Now when I hit Enter
and I get the help info.
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With the up arrow
and the down arrow,
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I can browse through the history
of all the commands that I did.
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If I have a longish
expression on the command line
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and I want to erase
the whole thing,
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I could start erasing it.
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Or I could press Control-C.
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That's probably
enough for today.
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To exit MATLAB, I either
look for the Quit MATLAB here
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or I can Apple-Q. Or from the
command line, I can type exit.