5 Vectors

5.1 Vectors

Vectors are ordered list of values.

Vectors can be of any data type
- numeric
- character
- logic
All items in a vector have to be of the same type
Vectors can be of any length

5.2 Defining vectors

A vector variable can be defined using

an identifier (e.g., a_vector)
on the left of an assignment operator <-
followed by the object to be linked to the identifier
in this case, the result returned by the function c
which creates a vector containing the element provided as input

a_vector <- c("Birmingham", "Derby", "Leicester",
  "Lincoln", "Nottingham", "Wolverhampton")
a_vector

## [1] "Birmingham"    "Derby"         "Leicester"     "Lincoln"      
## [5] "Nottingham"    "Wolverhampton"

5.3 Creating vectors

the operator :
the function seq
the function rep

4:7

## [1] 4 5 6 7

seq(1, 7, by = 0.5)

##  [1] 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0

seq(1, 10, length.out = 7)

## [1]  1.0  2.5  4.0  5.5  7.0  8.5 10.0

rep("Ciao", 4)

## [1] "Ciao" "Ciao" "Ciao" "Ciao"

5.4 Selection

Each element of a vector can be retrieved specifying the related index between square brackets, after the identifier of the vector. The first element of the vector has index 1.

a_vector[3]

## [1] "Leicester"

A vector of indexes can be used to retrieve more than one element.

a_vector[c(5, 3)]

## [1] "Nottingham" "Leicester"

5.5 Functions on vectors

Functions can be used on a vector variable directly

a_numeric_vector <- 1:5
a_numeric_vector + 10

## [1] 11 12 13 14 15

sqrt(a_numeric_vector)

## [1] 1.000000 1.414214 1.732051 2.000000 2.236068

a_numeric_vector >= 3

## [1] FALSE FALSE  TRUE  TRUE  TRUE

5.6 Any and all

Overall expressions can be tested using the functions:

any, TRUE if any of the elements satisfies the condition
all, TRUE if all of the elements satisfy the condition

any(a_numeric_vector >= 3)

## [1] TRUE

all(a_numeric_vector >= 3)

## [1] FALSE