What is vector data structure in R?

Vectors are sequence containers of the same type and used as data structures in multiple programming languages. In the R language, there are two major classifications of vectors:

1. atomic (homogeneous)
2. recursive (heterogeneous)

Atomic vs recursive vectors

As highlighted, when we pass a single value, it becomes a vector with a length of 1, and hence we are creating atomic vectors. Below on line #22, we are creating a recursive vector, list("a", 34L , 2:8). It contains an "a" character type at the first index. It contains 34L (integer type) at second index and 2:8 (vector type containing 2,3,4,5,6,7,8) at the third index.

In R, the default numeric value is double. To make it an integer (32bit), we can use L with it.

Common properties

1. Length: You can get the length of any vector using length() method.
2. Attributes: To extract additional arbitrary metadata, use attributes().
3. Type: To check the type of vector, you can use typeof() method.

Accessing vector elements

Elements can be accessed by using their indexes and square brackets. Indexes start with position 1 i.e., data[1]. Providing a negative value in the index drops that element from the result. TRUE, FALSE, 0 and 1 can also be used to index a vector.

Example

In line 2 of the code snippet below, we are creating vector data that contains the month name at each index.

• Line #4: In this line we’ve demonstrated indexing by using a vector containing index positions. Passing the vector of indexes c(2,3,6) we can access each index of vector data.
• Line #7: Here we see indexing using Boolean values. Passing a Boolean vector with equal length, each index will be marked either true or false. An index containing true will be accessed.
• Line #11: This is an example of accessing using negative index values. Passing a vector of negative index values. It will exclude specified indexes from results i.e., -2 and -5. Results will not include values at “Feb” and “May” indexes.

Declaring and defining vectors

Listed below are some useful methods to create vectors, either recursive or atomic types.

1. Creating vectors with c()

This is a generic method that combines argument values to generate a vector. All argument values are of the same type and the return type will be the same as the arguments.

2. Creating vector with seq()

This seq() method accepts from, to and increment values as an argument. In the example below, seq(5, 9, by= 0.4) will generate values from 5 to 9 by an increment of 0.4.

3. Creating vectors with : Operator

By using this : operator, we can create a vector of consecutive values. As in the example below, on lines 2, 6, 10 we are using a colon operator to initialize the vectors.

In most cases cat() and print() have the same behaviour but cat() is used for atomic types i.e., integer, double, character, raw etc. While the print() method is used for non-atomic types like a non-empty list and any type of object.