Home: 1. Basic Syntax

In this lesson we will review some of the basic syntax in R, including the following common operators:

<- assignment operator
> greater than operator
< less than operator
== equality operator
!= inequality operator
& and operator
| or operator

Syntax

Syntax in computer programming is a set of rules that defines the structure of a language, similar to how we have rules for grammar and spelling. If you write a sentence with incorrect spelling or grammar, the sentence may not make sense. If you write code without proper syntax, the code won’t be able to run and you’ll get an error message.

Example

In this example, we are trying to print the following famous coding statement: “hello world”.
In this first R chunk, we can see how to successfully print “hello world”.

To run the line of code below (aka R chunk) you can either push the green arrow pointing to the right or click on the line of code and push ctrl+enter (windows) or cmd+enter (mac).

print("hello world")

[1] "hello world"

In this second R chunk, we can see what happens if we have even the slightest mistake in our code. R recognizes “print”, but not “Print” with a capital P. This is an important lesson because it demonstrates that R (and many programming languages) are sensitive to capitalization. Therefore, if you run a line of code and get an error, it’s always a good idea to double check that you’ve spelled everything correctly.

Print("hello world")

Error in Print("hello world"): could not find function "Print"

Operators

Assignment Operator

In R, one of the most common operators is the “assignment operator” which looks like this arrow <-.
In most situations, it would also be acceptable to use the = sign, but in R, the arrow is the typical notation.
In this next example, we are assigning x to be 10, y to be 25, and z to be 100.
x, y, and z are stored as values (or variables) in our Environment.

Before you run the R chunk below, click on the Environment pane (usually located in the top right corner of RStudio). Watch what happens when you run the code below. If you’re unfamiliar with the Environment tab, I recommend watching my tutorial on Introduction to R.

x <- 10
x

[1] 10

y <- 25
y

[1] 25

z <- 100
z

[1] 100

As you can see, when you use the assignment operator, it saves the values (x, y, z) in your Environment. This means that R will remember these values.
To test this out, type “z” into your console and press enter and see what happens! Spoiler: it should return the value 100.

Greater or Less than Operators

> is the greater than operator.
< is the less than operator.
In this example, we will ask if x is greater than y?
Remember, we have x assigned to 10 and y assigned to 25. So, is 10 greater than 25? True or False?

x > y

[1] FALSE

Is x less than y?

x < y

[1] TRUE

Equality Operators

== is the equal-to operator.
We can think of the example below as “is x equal to y?”.
Notice, in this scenario R will return TRUE or FALSE and the values of x and y do not change.

x == y

[1] FALSE

x # x is still 10

[1] 10

Note here, we have a # followed by some text. A # in R indicates a comment. Any text that follows a # will not be evaluated. This is a great way to leave notes or comments for yourself.

Be careful not to confuse == and =.
If we instead had x = y, R doesn’t return anything, but the value of x has updated.

x = y # remember, this could also be x <- y
x # x is now 25

[1] 25

Here, we’ll just re-assign x to 10.

x <- 10

!= is the not-equal-to operator (opposite of ==).
We can think of the example below as: “Is x not equal to y, True or False?”.

x != y

[1] TRUE

The And Operator

& is the “and” operator.
We can think of this example in two parts: “Is z greater than 50?” AND “is z less than 200?”.
Remember, z is 100. So, is it true that 100 > 50 AND 100 < 200?
In order for this statement to be true, both pieces must be true.

z > 50 & z < 200

[1] TRUE

What about if we asked the following: is z > 50 AND is z > 200?

z > 50 & z > 200

[1] FALSE

The Or Operator

| is the “or” operator.
We can again think of this example in two parts: “is z greater than 50?” OR “is z greater than 200?”.
However, this time, in order for the statement (aka expression) to be true, only one of the parts needs to be true.
So, let’s test the same line of code we had in the last example but with an | operator instead of an & operator.

z > 50 | z > 200

[1] TRUE

Summary

In this lesson we learned about syntax in R and some of the most common operators (<-, >, <, ==, !=, !=, &, |).

We also learned a few useful tips, including how to run R chunks and how to leave comments using the #.

Exercises

In this exercise, we’ll compare the heights (in inches) of some amazing female artists: Jennifer Lopez, Taylor Swift, and Miley Cyrus.

Create three variables with each woman’s respective height (Jennifer = 64.57, Taylor = 70.87, Miley = 64.96). Save your three variables as jennifer, taylor, and miley.

Remember to use the assignment operator and make sure to run each line of code (or the entire code chunk) to make sure we save the variables to the environment.

Is Miley shorter than Taylor? Write 1 line of code that will return the answer as either TRUE of FALSE.

Are Miley and Jennifer the same heights?

Is Miley taller than both Jennifer and Taylor?

Is Miley taller than either Jennifer or Taylor?

1. Basic Syntax