A vector is a workhorse datatype of R and basic data structure in R. It contains elements of a homogenous data type. The data types can be logical, integer, double, character, complex or raw.

Creating a vector 

numeric_vector <- c(1, 2, 3)
character_vector <- c("fruits", "vegetables", "nuts")
logical_vector<- c(TRUE,FALSE,T,F)

Attributes of a vector

There are two important attribute of a vector:

A vectors length can be checked with length()

numeric_vector=c(1,2,3) 
length(numeric_vector)
[1] 3

A vector’s type can be checked with the typeof() function

x=c(1,"aa",TRUE,1.5)
typeof(x)
[1] "character"

Creating a vector using :operator

if we want to create a vector of consecutive numbers, the : operator is very helpful.

x=1:7
y
y=-3:3
y
[1] 1 2 3 4 5 6 7
[1] -3 -2 -1  0  1  2  3

In R, a function is a piece of code written to carry out a specified task. R Functions are called as objects because you can work with them exactly the same way you work with any other type of object. R Vector functions are those functions which we use in R vectors. For Example: seq(), rep().

Creating a vector using seq() function

More complex sequences can be created using the seq() function, like defining number of points in an interval, or the step size.

seq(1, 4, by=0.2)  
seq(0,50,by=5)
 [1] 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0
[1]  0  5 10 15 20 25 30 35 40 45 50

rep() function

rep() replicates the values in x. It is a generic function.

You can use the rep() function in several ways,just by changing the arguments.
To repeat the vector c(1,2,3) five times, use this code:

rep(c(1,2,3),times=5)
[1] 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3

We can also repeat every value by specifying the argument each, like this:

rep(c(1,0,0),each=2)
[1] 1 1 0 0 0 0

We can tell R for each value how often it has to repeat:

rep(c(1,0),times=c(2,3))
[1] 1 1 0 0 0

Naming a vector

We can assign names to vector members.

expenses=c(100,210,200,150,310,200,100)
days_vector=c("mon","tue","wed","thurs","fri","sat","sun")
days vector
names(expenses)=days_vector
expenses
mon   tue   wed thurs   fri   sat   sun 
 100   210   200   150   310   200   100

Combining/appending vectors

Vectors can be combined via the function c

n = c(2, 3, 5) 
s = c("aa", "bb", "cc", "dd", "ee") 
c(n, s) 
[1] "2"  "3"  "5"  "aa" "bb" "cc" "dd" "ee"

Vector Arithmetics

Arithmetic operations are performed member by member in a vector.
for example,suppose we have two vectors x and y.

x=c(1,2,3,4)
y=c(1,2,3,4)
z=x+y
z 
[1] 2 4 6 8

Then, if we multiply x by 5, we would get a vector with each of its members multiplied by 5. 

x*5
[1]  5 10 15 20

Similarly, for subtraction, multiplication, and division, we get new vectors via memberwise operations.

x-y
x*y
x/y
[1] 0 0 0 0
[1]  1  4  9 16
[1] 1 1 1 1

Recycling Rule

If two vectors are of unequal length, the shorter one will be recycled in order to match the longer vector. For example, the following vectors u and v have different lengths, and their sum is computed by recycling values of the shorter vector u.

v=c(1,2,3,4,5,6)
a=u+v
a
[1] 11 22 33 14 25 36

How to access elements of the vector?
We retrieve values in a vector by declaring an index inside a single square bracket “[]” operator. 

u[2]
u[1:3]
[1] 20
[1] 10 20 30
MatricesVectors