Data Structure in R

We will look at five basic data structures that are available in R.

Vectors

 

A vector is the simplest type of data structure in R. Simply put, a vector is a sequence of data elements of the same basic type. Members of a vector are called Components. The elements of a vector are all numbers, giving a numeric vector, or all character values, giving a character vector. A vector can be used to represent a single variable in a data set.

 

Factors

 

A collection of values that all come from a fixed set of possible values. A factor is similar to a vector, except that the values within a factor are limited to a fixed set of possible values. A factor can be used to represent a categorical variable in a data set.

 

Matrices

 
This is a two-dimensional structure (like a data frame), but one where all values are of the same type (like a vector).

A two-dimensional collection of values that all have the same type. The values are arranged in rows and columns. There is also an array data structure that extends this idea to more than two dimensions.

 

 Data frames

Most data sets consist of more than just one variable, so to store a complete data set we need a different data structure. In R, several variables can be stored together in an object called a data frame.A collection of vectors that all have the same length. This is like a matrix, except that each column can contain a different data type. A data frame can be used to represent an entire data set.

 

 Lists

A collection of data structures. The components of a list can be simply vectors--similar to a data frame, but with each column allowed to have a different length. However, a list can also be a much more complicated structure. This is a very flexible data structure. Lists can be used to store any combination of data values together.