Names and Objects

Remember information by giving it a name

The power of assignment

In R, and in computer programming in general, the most essential operation is to assign objects to names. By object, we then broadly mean any piece of information. a single number, a text, a list of numbers, and even an entire data set.

In plain terms, assignment is how you make R remember things by assigning them to a name. To assign an object to a name, we use the arrow notation: name <- value. For example:

x <- 2

Instead of using the arrow notation, you can also use the equal sign notation: name = object.

x = 2

We will in general always use the arrow notation. But if you encounter the equal sign notation, just remember that it’s the same thing.

By running the code x <- 2, you are saying: Assign the value 2 to the name x. Any objects that you assigned to names are stored in your Environment. You can see this environment in the top-right window, under the Environment tab. If you assigned 2 to x, you should see a table with in the left column the names (x) and in the right column a description of the object. For simply objects like numbers, this will just be the value (2).

From hereon, when you use the name x in your code, it will refer to the value 2. So when we run the code x * 5 (x times 5) it will print the number 10

x * 5
[1] 10

When running x * 5, R correctly prints the value 10. But why does it say [1] 10? The reason is that R always thinks of a number (or string) as a vector (i.e. list of values), that can have 1 or multiple values. The [1] indicates that 10 is the first (and only) value.

If you print a longer vector, you can see that R prints [...] at the start of each line, just to help you see the position of individual values. The following code generates a vector with numbers from 1 to 50

1:50
 [1]  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
[26] 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

Assigning versus printing

Notice that when you ran the code x <- 2, R didn’t print any values to the console (the bottom-left window). But when you ran x * 5, R did print the value 10. Basically, when you run code, and you DO NOT assign the result to a name, R will print the result to the console.

So the following code will NOT print the object ("I will not be printed") to the console, but will store it (you can see the name pop up in the Environment tab)

i_will_be_remembered <- "I will not be printed"

And the following object ("I will be printed") will be printed to the console, but not stored in the Environment.

"I will be printed"
[1] "I will be printed"

Assigning different types of objects

You can assign any type of object to a name, and you can use any name, as long as it starts with a letter and doesn’t contain spaces or symbols (but underscores are OK)

a_number = 5
my_cats_name = "Hobbes"

If you run this code and check you Environment (top-right), you should now see these name-object pairs added.

Assigning results

Till now we only directly assigned objects to names. This is convenient, but the power of assignment really shines when you use it to store results. For example, we can also do this.

x = 5 + 10

This a very simple example, but just think for a second what this allows us to do. Since we can assign anything to a name, we can break down any complicated procedure into multiple steps! For now, the key lesson is just to wrap your head around the syntax for assigning objects to names. This is fundamental to everything you will be doing in R (and in programming in general).

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