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[MUSIC PLAYING]

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SPEAKER: Well, hello, one and all,
and welcome to our short on the R

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console, which you can use to navigate
the files and folders on your computer

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as you write R programs.

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Now, odds are you're used to
a graphical user interface.

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You can click on files and folders.

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You can certainly do
that in RStudio, as well.

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But it's worth getting familiar
now with the console, which

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you can use to actually
access files and folders

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and create new files
and folders, as well.

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So here is the R console, with
this blinking cursor here.

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And everything we'll talk about today,
is also inside of the R documentation.

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So if I were to type in
something like this, ?files,

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I could actually open up the R
documentation on file manipulation.

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And you can get a reminder
of the kinds of functions

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we'll use today to create files,
remove files, rename them, and so on.

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So feel free to always use this
if you need a hand along the way

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while you're programming
live on your own.

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Now, let's figure out what
we're going to do here.

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I want to create a new program,
maybe one to say hello to the world.

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And to do that, I'll need to maybe make
some new files, make some new folders,

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and rename them and
change them along the way.

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So let's do just that and learn about
the kinds of commands and functions

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we can use to create
these files and folders.

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As we said before, R
gives you what's called

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a working directory, or the
folder that, by default,

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you'll create new files
and folders inside of.

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So if I were to type this
function here, getwd(), well,

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this would actually print
for me the working directory,

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where I currently am in
my computer's file system.

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So if I hit Enter, I'll see that I'm
currently in the Users/jharvard folder.

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OK, pretty good.

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I might also ask, well, what files
and folders are already here?

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To do that, I could type in
this function, list.files().

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Hmm, I get back character(0).

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And this actually means that
there are no files and folders

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inside of this directory,
so blank slate for now.

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Another alias or a name for
list.list.files() is this function here

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D-I-R, dir(), If I type dir(),
I also get the same result.

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It's the same function,
same functionality now,

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just different names for it, one
being shorter than the other.

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You can use them interchangeably.

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So we've seen where we are in our
file system, inside Users/jharvard,

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and there are no files or folders
inside of this working directory,

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but let's go ahead and maybe create one.

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So I might want to store
my program to say hello

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to the world inside of a folder.

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So how could I create a folder?

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Well, I could use a function
called dir.create().

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dir.create() will take as input,
the name of the directory,

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the folder I want to create.

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So I'll type in "hello" to be the name
of the folder in which I'll create this

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program to say hello to the world.

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Let me hit Enter now, and I'll
see nothing seems to happen.

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But if you look in your
graphical interface,

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over here, you might actually
see this folder now called hello.

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And I can even confirm this
in the R console directly.

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If I were to type either list.files()
or dir(), I could then see, well,

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I have a folder called hello
inside of my working directory,

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OK, so I have a folder, but
then how do I get into it

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to write, in this case, my program?

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Well, I could use another
function very similar to getwd(),

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but this one is called setwd().

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I want to change my working directory
to be this particular folder that I

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called hello.

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So I can type setwd() and give as
input, the folder I want to change to be

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my working directory.

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I'll type "hello" in this case.

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And this will work because hello is
part of my current working directory.

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I'll type Enter here.

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And now I'll see my working directory
seems to have changed up top.

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It used to be /Users/jharvard, but
now it's /Users/jharvard/hello.

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And I can confirm this using
getwd(), hit Enter here,

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and I'll see my new working directory.

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OK, So here I now am inside
of this hello folder.

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What I've done metaphorically now,
or actually really on my console, is

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I've taken this folder that I see here.

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I've clicked on it, and
I've gone inside of it.

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But of course, there are no files here.

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We need to first create our
file to say hello to the world.

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So I can use this function
that we've seen before,

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file.create() that will create for me
now a new file of any kind that I want.

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I could maybe make a file to say
hello to the world by typing "hello.R"

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hitting Enter, and hmm, well,
I see the file over here.

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But I did make a typo.

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So not to worry.

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I can use a function to
rename this file too.

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So if I type list.files(), I'll
see my misspelled file name.

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But thankfully, we actually
can use file.rename(),

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another function here that
takes as input two arguments.

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The first being the file
name that exists currently,

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and the next being the file
name we want to change to.

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So this says rename hello.R
L, to hello.R with two L's.

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I'll hit Enter now, and I'll see
true, meaning everything's gone well.

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And now, if I actually look
inside of my hello folder, well,

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I should hopefully see the properly
spelled hello.R. And again,

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if I were to type either list.files()
or dir(), I should now see hello.R,

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pretty good.

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And as a side note here,
as I've been moving,

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I've been kind of clearing
my console as I go.

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And to do that, there's
a simple shortcut,

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CTRL-L that can clear
your console for you

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so you can start fresh every time, OK.

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So here I have hello.R. Why don't I
actually go inside of it by clicking

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on this file here and typing in,
print("hello world"), just like this.

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As we've seen, I could run this R code
by clicking on the source button here.

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Source means run this program.

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So I could do just that here,
source, and I'll see hello world down

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in the console.

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But I could even do this.

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I could run this program
from the console too.

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I could type source
myself, and then pass

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in the name of the file I want to
run, in this case, hello.R, hit Enter.

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I'll see hello world.

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Now, common mistake is that if
you wanted to run some file,

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but you're in the wrong
working directory.

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So always check if the file you want
to run is in your working directory

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by typing something
like this, list.files,

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and you're confirming that
you see that particular file.

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Or if it's not there,
go ahead and use setwd

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to set your working directory to where
you can find that particular file.

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All right, so I have my program here.

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I can run it just as well.

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And let's say I'm done.

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I don't want this program anymore.

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I might want to delete
what I've done here.

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So I'll go ahead and x this out.

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My file is still there, of
course, if I type list.files,

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but now I might want to remove
this file, for instance.

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Well, I could, first,
try to remove maybe

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the file and the folder it's inside
of to kind of clean things up.

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Well, right now, I don't see
that folder hello anymore.

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I'm actually inside of it.

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So to get back up from it,
I can use setwd, but now

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pass in the special kind of argument.

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I'll type in dot dot.

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And dot dot means move my working
directory up one individual level.

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So from, in this case,
hello to jharvard.

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I'll hit Enter here.

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And notice how if I type getwd, well now
I see I'm back in the jharvard folder.

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I've moved up one level
thanks to dot dot,

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which has this very
special meaning saying

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move me up one particular directory.

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All right, so if I type list.files
now, I actually see the hello folder.

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And to remove this, well, I could try
this file.remove("hello"), hit Enter.

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Hmm, And I'll actually see false,
meaning that something didn't work,

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and I'll see a warning message that
says, it cannot remove file hello,

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reason being directory not empty.

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And that's true.

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Because as we see here, hello still
has this file hello.R inside of it.

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So to remove this
directory, we'll actually

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first need to remove the hello.R file.

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So I could use file.remove,
but now first remove hello.R.

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I could type
file.remove("hello/hello.R").

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And this is saying, go into the hello
folder, find for me that hello.R file,

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and remove it from that folder.

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I'll hit Enter here, and I'll see
true, seemed to have worked OK,

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and now if I type file.remove("hello"),
I can remove that directory that is now

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empty.

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I'll hit Enter here, and
if I type list.files,

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well, I'm back to having no files
and folders inside of this directory.

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Now, one other handy trick here.

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Why don't I go back and
recreate what I had before?

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I'll say, dir.create("hello").

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And then I'll say, file.create.

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I can actually create files
from above the given folder.

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If I wanted to create hello.R
inside of the hello folder

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but not change my working directory,
I could type out the path to it.

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I could say, well, it's
inside the hello folder,

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and then I want to
make this file hello.R.

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So to be clear, I'm going
first to the hello folder,

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and this slash means inside that folder,
go ahead and create hello.R for me.

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I'll hit Enter and hopefully,
see that that seemed to work.

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I have true here.

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And if I confirm this
on the right-hand side,

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I can actually see hello.R as well.

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OK, so I've created these files again.

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But now, you might catch on, do you
have a folder with a lot of files?

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It could be really annoying
to go through and clean up

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each one individually using
file.remove, file.remove, file.remove.

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So actually, R provides
us with another approach

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to remove a directory and all
of its contents in one command.

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So this is a bit of a
dangerous one but also useful

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if you want to clean things up quickly.

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So this function is
called unlink, unlink.

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And I can type, as input,
the first argument being

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the folder I want to remove.

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Now, there is a special parameter to
unlink called recursive, recursive.

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Recursive means, basically, go into
this folder, and any subfolders

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and remove those, unlink them as well.

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And if I set recursive to
true, what this will do,

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is first look in the hello
folder, and then descend

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into any folders inside
the hello folder,

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and descend into any folders
inside those folders and so on,

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and go all the way down
to remove or unlink

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all the files and folders inside of a
particular one beginning with hello.

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So if I hit Enter now, and I type
list.files, I'll see, in one command,

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I've removed hello.R
and the hello folder,

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all thanks to unlink with this
recursive parameter set to true.

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So this was a brief overview of how you
can use the console to write programs

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in R, change your files, change your
folders, and build things up as you go.

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I'm excited to see what you'll
create using the R console.

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We'll see you next time.

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