Vector

1. Vector

In the previous notebook we worked with creating object, which stores 1 value to an object. We are occasionally interested in storing several values to an object.

Let’s imagine that we would like to analyze the test scores of five students. We can create five variables:

student1 <- 90
student2 <- 85
student3 <- 86
student4 <- 92
student5 <- 93

and the compute the average by using the following code:

total <- student1 + student2 + student3 + student4 + student5
average <- total / 5

However, dataset in the real world can have many elements, and it is unrealistic to create variables for each individual element. Instead, we can create a vector that includes multiple values.

Vector is one of the most important concepts in R programming, and it can be created by using c() function.

For example:

score <- c(90, 85, 86, 92, 93)
score

## [1] 90 85 86 92 93

2. Vector Applications

2-1. Compute average

The function mean() can get the average value in the vector:

mean(score)

## [1] 89.2

2-2. Compute sum

The function sum() can get the sum of values in the vector:

sum(score)

## [1] 446

2-3. Access element in a vector

We write: vector_name[number]

to access the element in the vector. For example:

# Acess the 1st element in the score vector
score[1]

## [1] 90

2-4. Access multiple elements

Instead of specifying 1 number, we can write number1:number2 inside [ ] to access multiple elements.

For example:

score[2:4]

## [1] 85 86 92

This will return a vector of elements from score[2] to score[4].

2-5. Change element in a vector

We can also change 1 element in a vector in the original list instead of creating a new one by specifying

vector_name[number] <- element

For example:

score <- c(90, 85, 86, 92, 93)
score[1] <- 100
score

## [1] 100  85  86  92  93

2-6. Add an element to a vector

We can add an element at the end of the vector through the append() function, which can be written as:

append(vector_name, element)

For example.

score <- c(90, 85, 86, 92, 93)
score <- append(score, 0)
score

## [1] 90 85 86 92 93  0

2-7. Length of vector

We can get the length of vector through length() function. For example,

number <- c(1, 2, 3)
length(number)

## [1] 3

2-8. Combine multiple vectors

Just like how we used c() to create a vector, we can combine vectors by using the same function. For example:

a <- c(1,2,3)
b <- c(11,12,13)

vec <- c(a,b)
vec

## [1]  1  2  3 11 12 13

Vector is a very important concept in R programming and we will be frequently using the concept in the future labs.