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You should have already
downloaded and installed

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R on your computer.

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If you have not downloaded
and installed R yet,

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please follow the instructions
on the course website

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before continuing
with this lecture.

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Once you've installed R,
go ahead and start it.

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You should see the R
console like we see here.

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This is where we'll type
commands and perform

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data analysis.

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In this course, we'll mostly
be working in the R console,

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but sometimes you'll
also want to use

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what are known as
"script files."

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We'll see an example
of how to use a script

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file at the end of this lecture.

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In your R console, you'll always
type commands after the arrow,

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or "greater than" sign.

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Let's start with some
basic calculations.

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So with your cursor
at the arrow,

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let's type 8, and then the
star symbol for "times,"

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the number 6, and hit Enter.

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You should see the
result 48, or 8 times 6.

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In this way, R can be used
as a basic calculator.

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We can perform many other
basic calculations, like 2,

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"raised to the power," by typing
the carrot symbol, and then

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the number 16,
and hitting Enter.

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You should see the result
65,536-- or 2 the power 16.

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Note that each of the results
here are labeled with a 1

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in brackets.

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This is just R's way
of labeling the output

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and we can safely ignore it.

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If you type something
in your R console

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but don't finish it
properly-- for example,

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try typing 2 and
the carrot symbol,

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and hitting Enter-- R
will show you a plus sign

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and will wait for you
to finish the command.

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You can either finish the
command-- in this case,

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by typing a number--
or you can hit Escape,

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and R will take you
back to the arrow sign.

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So if you ever see a plus
sign while working in R,

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it means that R is waiting
for you to finish the line.

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If you're not sure
how to finish it,

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you can always just hit Escape.

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A nice feature of
the R console is

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that you can scroll through
your previous commands

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by using the up and down
arrows on your keyboard.

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If you hit the up
arrow three times,

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you should go back to
the 8 times 6 command.

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If you hit Enter, you can
run this command again.

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You could also adjust
previous commands.

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Hit the up arrow again to go
back to the 8 times 6 command.

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This time, delete the 6,
type a 10, and hit Enter.

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We'll use this
approach to re-run

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or adjust commands many
times in this class.

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Generally, R works in terms
of functions and variables.

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A function can take in
several arguments, or inputs,

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and returns an output value.

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An example is the square
root, or sqrt, function.

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In your R console,
type sqrt, and then

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in parentheses, the
number 2, and hit Enter.

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The function is sqrt, the input,
or argument, is the number 2,

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and the output is 1.414214.

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There are thousands of
functions in R. Some of them

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are built into R--
like this one--

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and some can be added in by
installing packages, which

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we'll do several
times in this class.

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Another example of a function
is the abs, or absolute value

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function, which returns the
absolute value of a number.

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So if we type abs and then
in parentheses negative 65

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and hit Enter, we should get
the result 65 as our output.

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You can get help on
any function in R

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by typing a question mark
and then the function name.

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So if we type ?sqrt
and hit Enter,

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you should see the R Help
Page for the sqrt function.

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The help pages are
often very useful,

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and if you want to learn
more about a function,

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you should refer to
the help page in R.

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Now, get rid of the Help Page,
and go back to your R console.

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Suppose we now want to save
the output of a function.

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We can do this by
saving it to a variable.

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In your R console, type
SquareRoot2 and then an

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equals sign, and then sqrt, and
in parentheses the number 2.

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And hit Enter.

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Now you don't see
the output of sqrt(2)

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because we saved it to the
variable named "SquareRoot2."

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You can see the value of a
variable by typing its name

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and hitting Enter.

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So type SquareRoot2 exactly how
you typed it before, and hit

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Enter.

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You should see that it
takes the value 1.414214.

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SquareRoot2 is a
name that we created,

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and we could have named
it many other things.

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Generally, you have
a lot of freedom

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in naming your variables, but
there are a couple basic rules.

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One is that you should not
use spaces in variable names.

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If you want to easily separate
words in a variable name,

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popular strategies are using
a mix of capital and lowercase

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letters-- as we did
here-- or to separate

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the words using periods.

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Another basic rule is
that you should not

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start variable
names with a number.

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Keep in mind that variable
names in R are case-sensitive.

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Capital and lowercase letters
are seen differently by R.

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When we created our
variable SquareRoot2,

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we used the equals
sign for assignment,

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or to assign the
value of sqrt(2)

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to the variable
named SquareRoot2.

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You could instead use a
"less than" sign with a dash.

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For example, let's create a
new variable called HoursYear,

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and then type the less
than sign and a dash,

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followed by 365 times 24.

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If you hit Enter and then type
HoursYear to look at its value,

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you should see 8,760-- or the
number of hours in a year.

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By doing this, the less
than sign and the dash

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did the exact same
thing as it would

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have done if we used
the equals sign.

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In this course, we'll
typically use the equals sign.

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But if you see this less
than sign and a dash used,

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keep in mind that it means the
same thing as an equals sign.

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Lastly, if you type ls and then
empty parentheses in your R

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console and hit
Enter, you should

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see a list of all
of the variables

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that you've created in
your current R session.

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Here, we've created
two variables--

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HoursYear and SquareRoot2.

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This can be useful if you
forget exactly how you

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typed a variable name.

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These are our basic building
blocks in R-- functions,

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like square root and absolute
value, and variables,

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like HoursYear and SquareRoot2.