Basic data types

R Programming works with numerous data types, including

  • Scalars
  • Vectors (numerical, character, logical)
  • Matrices
  • Data frames
  • Lists

Basics types

  • 4.5 is a decimal value called numerics.
  • 4 is a natural value called integers. Integers are also numerics.
  • TRUE or FALSE is a Boolean value called logical.
  • The value inside " " or ’ ’ are text (string). They are called characters.

We can check the type of a variable with the class function

Example 1:

# Declare variables of different types
# Numeric
x <- 28
class(x)
## [1] "numeric"

Example 2:

# String
y <- "R is Fantastic"
class(y)
## [1] "character"

Example 3:

# Boolean
z <- TRUE
class(z)
## [1] "logical"

Variables

Variables store values and are an important component in programming, especially for a data scientist. A variable can store a number, an object, a statistical result, vector, dataset, a model prediction basically anything R outputs. We can use that variable later simply by calling the name of the variable.

To declare a variable, we need to assign a variable name. The name should not have space. We can use _ to connect to words.

To add a value to the variable, use <- or =.

Here is the syntax:

# First way to declare a variable:  use the `<-`
name_of_variable <- value
# Second way to declare a variable:  use the `=`
name_of_variable = value

In the command line, we can write the following codes to see what happens:

Example 1:

# Print variable x
x <- 42

Example 2:

y  <- 10
y
## [1] 10

Example 3:

# We call x and y and apply a subtraction
x - y
## [1] 32

Vectors

A vector is a one-dimensional array. We can create a vector with all the basic data type we learnt before. The simplest way to build a vector in R, is to use the c command.

Example 1:

# Numerical
vec_num <- c(1, 10, 49)
vec_num
## [1]  1 10 49

Example 2:

# Character 
vec_chr <- c("a", "b", "c")
vec_chr
## [1] "a" "b" "c"

Example 3:

# Boolean 
vec_bool <-  c(TRUE, FALSE, TRUE)
vec_bool
## [1]  TRUE FALSE  TRUE

Example 4:

We can do arithmetic calculations on vectors.

# Create the vectors
vect_1 <- c(1, 3, 5)
vect_2 <- c(2, 4, 6)
# Take the sum of A_vector and B_vector
sum_vect <- vect_1 + vect_2
# Print out total_vector
sum_vect
## [1]  3  7 11

Example 5:

In R, it is possible to slice a vector. In some occasion, we are interested in only the first five rows of a vector. We can use the [1:5] command to extract the value 1 to 5.

# Slice the first five rows of the vector
slice_vector <- c(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
slice_vector[1:5]
## [1] 1 2 3 4 5

Example 6:

The shortest way to create a range of value is to use the: between two numbers. For instance, from the above example, we can write c(1:10) to create a vector of value from one to ten.

# Faster way to create adjacent values
c(1:10)
##  [1]  1  2  3  4  5  6  7  8  9 10

Arithmetic Operators

We will first see the basic arithmetic operations in R. The following operators stand for:

Operator Description
Addition
Subtraction
Multiplication
/ Division
^ or ** Exponentiation

You can easily copy and paste the above R code into Rstudio Console. The output is displayed after the character #. For instance, we write the code print(‘Hello world’) the output will be ##[1] “Hello world”.

The ## means we print an output and the number in the square bracket ([1]) is the number of the display

The sentences starting with # annotation. We can use # inside an R script to add any comment we want. R won’t read it during the running time.

Example 1:

# An addition
3 + 4
## [1] 7

Example 2:

# A multiplication
3 * 5
## [1] 15

Example 3:

# A division
(5 + 5) / 2
## [1] 5

Example 4:

# Exponentiation
2^5
## [1] 32

Example 5:

# Modulo
28 %% 6
## [1] 4

Logical Operators

With logical operators, we want to return values inside the vector based on logical conditions. Following is a detailed list of logical operators available in R

Operator Description
< Less than
<= Less than or equal to
> Greater than
>= Greater than or equal to
== Exactly equal to
!= Not equal to
!x Not x
x & y x AND y
isTRUE(x Test if x is TRUE

The logical statements in R are wrapped inside the [ ]. We can add many conditional statements as we like but we need to include them in a parenthesis. We can follow this structure to create a conditional statement:

variable_name[(conditional_statement)]

With variable_name referring to the variable, we want to use for the statement. We create the logical statement i.e. variable_name > 0. Finally, we use the square bracket to finalize the logical statement. Below, an example of a logical statement.

Example 1:

# Create a vector from 1 to 10
logical_vector <- c(1:10)
logical_vector > 5
##  [1] FALSE FALSE FALSE FALSE FALSE  TRUE  TRUE  TRUE  TRUE  TRUE

In the output above, R reads each value and compares it to the statement logical_vector > 5. If the value is strictly superior to five, then the condition is TRUE, otherwise FALSE. R returns a vector of TRUE and FALSE.

Example 2:

In the example below, we want to extract the values that only meet the condition ‘is strictly superior to five’. For that, we can wrap the condition inside a square bracket precede by the vector containing the values.

# Print value strictly above 5
logical_vector[(logical_vector > 5)]
## [1]  6  7  8  9 10

Example 3:

# Print 5 and 6
logical_vector <- c(1:10)
logical_vector[(logical_vector > 4) & (logical_vector < 7)]
## [1] 5 6
 

A work by Gianluca Sottile

gianluca.sottile@unipa.it