2.4 Expressions, Objects and Symbols

The R code is composed by expressions. Some examples of expressions:

  • Assignments
  • Conditional sentences
  • Arithmetic operations
  • …

Expressions are made up of objects and functions. Each expression is separated from another by a new line or semicolon (;).

The R code manipulates objects. Some examples of objects:

  • Vectors
  • Lists
  • Functions
  • …

Formally the variable names in R are called symbols. Thus, we assign the object to a symbol of the current environment. The environment is formed by the set of symbols in a certain context.

2.4.1 Some examples to start with

We can use R for many things, but there are certain basics that need to be learned. When we enter a code in the R console, this code will provide us with an output. Let’s look at an example: If we enter a number or a word, R will return the same number or word.

23
## [1] 23
"Baby Yoda"
## [1] "Baby Yoda"

Each of these codes we have generated is interpreted by R, sent to our computer in a low level language, and returned in an understandable format for us.

Each code can be understood as an object (not stored) that R is interpreting for us. If we want to store that objects in our computer RAM to use them later in the same R session we need to create an assignment (we assign something to a symbol). Example:

my_number = 23
my_character = "Baby Yoda"

So we can use them later. For example, let’s just print them:

print(my_number)
## [1] 23
print(my_character)
## [1] "Baby Yoda"

Notice that to assign something to a symbol we can use = or <-:

my_number = 23
my_character = "Baby Yoda"
print(my_number)
## [1] 23
print(my_character)
## [1] "Baby Yoda"