R Programming Basics

  Generally, while doing programming in any programming language, you need to use various variables to store various information. Variables are nothing but reserved memory locations to store values. This means that, when you create a variable you reserve some space in memory.

You may like to store information of various data types like character, wide character, integer, floating point, double floating point, Boolean etc. Based on the data type of a variable, the operating system allocates memory and decides what can be stored in the reserved memory.

In contrast to other programming languages like C and java in R, the variables are not declared as some data type. The variables are assigned with R-Objects and the data type of the R-object becomes the data type of the variable. There are many types of R-objects. The frequently used ones are −

• Vectors
• Lists
• Matrices
• Arrays
• Factors
• Data Frames

The simplest of these objects is the vector object and there are six data types of these atomic vectors, also termed as six classes of vectors. The other R-Objects are built upon the atomic vectors.

Logical Data Type

TRUE, FALSE

v <- TRUE

print(class(v))

 

Numeric Data Type

12.3, 5, 999

 

v <- 23.5

print(class(v))

 

Integer Data Type

2L, 34L, 0L

v <- 2L

print(class(v))

Complex Data Type

 

3 + 2i

v <- 2+5i

print(class(v))

 

Character Data Type

 

'a' , '"good", "TRUE", '23.4'

v <- "TRUE"

print(class(v))

 

Raw Data Type

 

"Hello" is stored as 48 65 6c 6c 6f

v <- charToRaw("Hello")

print(class(v))

 

Vectors

When you want to create vector with more than one element, you should use c() function which means to combine the elements into a vector.

# Create a vector.

apple <- c('red','green',"yellow")

print(apple)

# Get the class of the vector.

print(class(apple))

Lists

A list is an R-object which can contain many different types of elements inside it like vectors, functions and even another list inside it.

# Create a list.

list1 <- list(c(2,5,3),21.3,sin)

# Print the list.

print(list1)

Matrices

A matrix is a two-dimensional rectangular data set. It can be created using a vector input to the matrix function.

# Create a matrix.

M = matrix( c('a','a','b','c','b','a'), nrow = 2, ncol = 3, byrow = TRUE)

print(M)

Arrays

While matrices are confined to two dimensions, arrays can be of any number of dimensions. The array function takes a dim attribute which creates the required number of dimension. In the below example we create an array with two elements which are 3x3 matrices each.

# Create an array.

a <- array(c('green','yellow'),dim = c(3,3,2))

print(a)

Factors

Factors are the r-objects which are created using a vector. It stores the vector along with the distinct values of the elements in the vector as labels. The labels are always character irrespective of whether it is numeric or character or Boolean etc. in the input vector. They are useful in statistical modeling.

Factors are created using the factor() function. The nlevels functions gives the count of levels.

# Create a vector.

apple_colors <- c('green','green','yellow','red','red','red','green')

# Create a factor object.

factor_apple <- factor(apple_colors)

# Print the factor.

print(factor_apple)

print(nlevels(factor_apple))

Data Frames

Data frames are tabular data objects. Unlike a matrix in data frame each column can contain different modes of data. The first column can be numeric while the second column can be character and third column can be logical. It is a list of vectors of equal length.

Data Frames are created using the data.frame() function.

# Create the data frame.

BMI <-    data.frame(

   gender = c("Male", "Male","Female"), 

   height = c(152, 171.5, 165), 

   weight = c(81,93, 78),

   Age = c(42,38,26)

)

print(BMI)