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YOSSI FARJOUN: This is
Dr. MATLAB, lecture two,

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The Command Prompt.

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If you're like me,
you'll find yourself

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on the command line a lot
when you're working MATLAB,

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so it's important to
know how to get around

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on the command prompt.

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The first thing I want to show
you is how to use the arrows.

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Say I want to plot something.

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So I want to plot sin of 2x
between 0 and pi on 200 points.

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This is what I type.

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Of course, I typed
it with a typo.

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I forgot to put
the multiplication

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sign between the 2
and the x up here.

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So we've already seen
in the previous lecture

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that instead of typing
the whole thing,

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I press the up command,
the up arrow, which

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brings up the previous command.

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And then with the left
arrow, I can place the cursor

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where I need it to be
and insert the asterisk.

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I forgot to put the
semi-colon, so again, I

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press up at the semi-colon
and now I have what I wanted.

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Now I plot x and y
and I get my plot.

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I'll put it into the window.

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Here it is.

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Great.

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Now unlike this plot, I
want to see the points,

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so I'm going to press up
and modify the plot command.

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And now I see the point.

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And I still don't see the point
because I plotted to many.

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So I, again, pressed
the up command.

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I know I can press
the up command twice

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to reach this line,
but what I want

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to show you is what happens
when you press the up

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command after I started
typing x equals.

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See this x equals is the
same as this x equals here.

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When I press up, the first
line that starts with x equals

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will show up.

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Here it is, if I
press up again, it

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will be the one
without the semicolon.

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If I press up again, it will be
the one without the asterisk.

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Let me go back down
to the one I want.

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This is the one I want.

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Now I want to change this 200
to something smaller, say five.

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So I could press the left area
until I reached there, and put

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50 points.

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And now plot again p, up, plot.

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Now 50 points.

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But here is a faster
way to get to that 50.

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Again, x, up-- now I
want to get to the 50,

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so instead of moving
with the left,

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I will move with
control left, and that

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moves one word at a time.

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In this case, it's
not a big difference,

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but sometimes it can be.

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See, it skips the whole word.

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It's skipping pi, it's
skipping linspace,

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it's skipping the whole 50.

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Let me put a 20 here.

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And now I want to
plot red points.

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And I have that.

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Another thing you can
do on the command line

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is to use Control-A. Control-A
for the beginning of the line,

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to move the cursor to the
beginning of the line,

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and Control-E to move the
cursor to the end of the line.

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Control-A for the beginning
of the line, Control-E

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for the end of the line.

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You can also cut and paste.

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With a shift, I select
Command-C to copy.

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Let's start a new line,
Command-V to paste.

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Depending on the
operating system,

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those commands might
be a bit different.

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Another thing you
might want to look at

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is the tab completion property.

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So if I start typing linspace,
I type lin s and now I hit Tab.

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MATLAB will show
all the commands

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it knows that start with
Lin s, in this case,

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linsolve and linspace.

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Of course the one
I want is linspace.

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If I want to find
help on this, I

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can press Control-A, move to
the beginning of the line,

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add help, add help,
and then hit Enter.

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Of course I can't see anything,
so I'll close this window.

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And here is the
help on linspace.

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And these are the two
ways you can use linspace.

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You give it the lower
and the upper limit,

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that gives you 100
points, equally

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spaced between those two.

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Or you give the
lower and upper limit

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and how many points
you want, and it

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get you that many points.

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For example, linspace,
0 to 10, five points.

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Here are five points equally
space between 0 to 10.

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Another thing that the help
file shows you are related

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commands that you might
want to read up on.

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So I encourage you to read
up on logspace and the colon

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function--

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it's actually the
colon operator,

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which is a very
complicated help file--

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and see why linspace is
related to colon and logspace.

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Another important feature
of the command line

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is the use of Control-C.
So it has two main things.

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For example, if you
have typed something,

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let's say I've
typed this, and I've

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decided I don't want
any of it, I actually

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went to do something else.

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So what I should do is
clear the whole line.

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I don't even want
to execute this.

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So to clear the whole
line without executing it,

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I'm going to press Control-C.
That clears that line.

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Control-C can also be used
to abort certain operations.

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For example, if I say x equals
1 while 1x equals x plus 1.

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So this is going to
add x all the time.

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As you see, x is
going to be growing

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and growing and growing
and growing forever.

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Now I want to stop
this at some point.

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So to stop it, really
the only thing I can do

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is to press Control-C. You
see while it's running,

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MATLAB says that it's busy.

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Sometimes it will be busy
and you won't even see it.

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Let's try that again.

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X equals 1 while 1--

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now I'll do it with a semicolon,
so I'll suppress output,

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but it will still be doing it.

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End.

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So now MATLAB is busy.

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It's not typing
anything on the screen,

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but it's doing the
same calculation

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that you saw before, except
it's not printing it out.

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Again, to abort this,
we press Control-C.

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You find out what x we got to.

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We counted quite high.

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We counted much higher
than here because we

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didn't have to display.

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If you're typing some other
command with a multi-line,

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i equals 1 to 100, j equals
i plus 2, for example.

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And midway through
that statement,

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you've decided
that you don't want

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to do it, again just
as before, pressing

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Enter is not going to help you.

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You're not going to get a
command prompt in this case.

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You can end it with an end
because you started with a for,

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or you could just
press Control-C.