Lesson 3.7: Scripts - MATLAB Video Lecture | Introduction to Programming with MATLAB - IT & Software

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There's a second kind of m-file
that we haven't covered yet.
It's an m-file that doesn't
have a function in it.
This kind of m-file is called a "script".
A script is just a collection
of MATLAB commands.
If you type the name of
the script's m-file and
hit Enter,
MATLAB simply executes these commands,
one by one, as if you typed them
into the command window yourself.
It's important to note that a script
is very different from a function.
First, a script never returns a value or
accepts input arguments.
And second, the scope of the script
is the scope of the Command Window.
So commands in a script access variables
that are already in the Command Window
workspace.
And they can put new variables into
the workspace with assignments,
just as you do when you're giving
commands in the Command Window.
Let's do a very simple example.
I'm going to make a script
called example_script.
[CLICKING]
MATLAB tells us that
this thing doesn't exist.
Do we want to create it?
I'll say yes, and I'm going to put,
"Do not show this prompt again."
Okay, we see a tab show up here
with the name example_script.
We got a blank page.We can type it in.
Before I do,
note that I've cleared the Workspace, so
there are no variables over here.
So I'm going to make a variable
called x by setting x equal to 5,
and there we see x is in the Workspace.
You'll see why I did that in a minute.
And I'm going to put two more variables
there with this script, y and z.
I'm going to do that with two assignment
statements: y equals x plus 3.
I think I'll leave that semicolon off,
and z equals 2 times y.
Not a very exciting script, but it'll do.
Now, back here in the Command Window,
to run the script, I just type the name of
the script, which is example_script,
[CLICKING]
and hit Return.
[CLICK]
The first statement in the script
accessed x over here in the Workspace.
So, you know that it has access to x.
And each command, the first one and
the second one, put a new variable
over here in the workspace, y and z.
MATLAB printed y's value to the Command Window because I didn't put a semicolon
up here at the end of the command.
That happened just as it would have if
I had typed that command directly into
the Command Window.
So when would you use a script?
Well, you'd use it when you want MATLAB to
repeat a set of commands in the Command
Window many times, and
you don't want to type them many times.
You tell MATLAB what's supposed to happen,
just like a script says what's supposed to
happen in a play or a movie,
by writing a script.
Okay, let's make one more script,
called endLessonThree.
I'll use the edit command just as I
did when I wanted to make a function.
[CLICKING]
And I'm going to put three
commands in this one.
[CLICKING]
We'll look at the function
fprintf in the next lesson.
It just prints out,
"This concludes Lesson 3."
The command, pause,
with that 5 as an input argument,
pauses for five seconds before
the next command is executed.
We need it here, because without it,
you won't have time to see the output
from fprintf before MATLAB quits.
Okay, let's run it.
end
Lesson
Three
Return
Oh, okay, I'd better hurry.
Goodbye, I'll see you in Lesson Fo.
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