Reading .csv files into RStudio

Hi. In this video,
I'm going to show you how you can read

in, CSV files, data files into R

so that you can do your, data analysis.

The first thing you need to do
is to set your working directory.

That is something that was described
and talked about in a previous video.

So navigate to the folder of wherever

the data set
you want to bring into R is located.

And I have already done so
because the data set I want to bring into

R is called MRI, dot, CSV.

Okay.

So if I want to bring in a CSV file,

CSV stands for comma separated values.

Usually it is opened up in a program
like Excel.

If I want to bring this data file into R,

I will use the read dot csv function.

And inside

the parentheses
I will put the name of the data.

And R is case sensitive.

So you need to make sure you spell it
exactly how it is.

Saved as underscores spaces anything.

And then you always need to include
the file extension

which is dot csv.

Okay.

Let's go ahead and run this
and see what happens.

This is also really nice and looks good.

So it looks like it read in our data
just fine.

And it saw here.

Oh look these are column titles.

So this is if you saw the first video
that I did previously, this is something

that's different between the readcsv
function and the read table function.

If your data

notice like what
if I did something like oh, sorry.

Wrong spot.

If I said this

command, I'll explain what this means
in a second.

Notice what R does.

It interprets

this very first line of code to be

an observation rather than, though
not this very first line.

Okay.

And interprets the first line of the data
to be an observation of data,

when in fact it really is

the titles of your columns
or the names of all of your variables.

ReadCSV is smart
and knows that most likely

your data is going to
have what we call a header.

But if your data happens
to not have a header.

So pretend that this first line
was actually data, but you wanted to

still be able to refer to the columns
as column one, two, three, four.

You could say header equals false, meaning
I don't have a header.

So please
assign them one, two, three, four, etc.

if you do have a header.

In our case we do

make sure to type out header equals true.

And notice what happens is that

R is able to notice that

the first line of your data
was the column titles.

And that is to not treat it
as an observation of data.

Good practice is to always
include this header argument,

and say header equals true or false
no matter what.

Notice also that I had to do in all caps.

If I try and just do capital T

or thinks I'm writing
just like the word true,

and it's not actually meaning internally,
like a logical value called true.

So I need to have it in all caps.

You can also do just the letter T

or just the letter F for true and false,

but it's better practice
to write out the entire word.

Okay, so this is nice that

you can bring in your CSV file into R,

but in order to do much
of anything with it, we need to kind of,

we need to save it into our environment

so that we can do further analysis
with it.

So rather than just running
just this readcsv line

in front of it, put, give this data,

set a name that you, that you can call it,
call it whatever you want.

I'm going to call it MRI, AI data.

And then in between the name
and this command,

you're going to put in what we call
the assignment operator.

And it is a less than sign and a dash.

What this means
is this little piece of code right here.

ReadCSV header equals true.

What that did is
it brought that data and said here it is.

But it didn't
actually do anything with it.

So what it's going to do is it's
going to take this data and store it.

And it kind of looks like it's like
pushing the arrow is pushing into here.

It's going to take this data and store it
in a little box called MRI data.

If we run this line of code

notice what happens over here
in our global environment.

It now shows hey,

you have now stored a data
set here in R called MRI data.

There's 15 observations and 11 variables
which is true.

We have 15 observations and 11 variables.

And now you should be able to do use.

You can just refer to the data by whatever
name you called it which is MRI data.

And R will always know,
hey, that's the data set

I'm supposed to be using whenever,

you type MRI data.

So that is how you can read in

dot CSV files into R

and how you can
then save it into your environment

so that you can do further, data
analysis, work with it.

Don't forget to set your working directory
at the very beginning,

and then remember that
R is case sensitive.

And to not forget the header argument.

And that
should be everything that you need.

Good luck and have fun. And r.