Vectors

Vectors allow us to store more values inside one. Vactors can be ow only one type. It might seem useless but will be awesome when we get to looping, data.frames simlulations, randomising etc.



In [20]:

    
str1 = "I"
str2 = "am"
str3 = "great"
num1 = 0
num2 = -5
num3 = pi

string_vec = c(str1, str2, str3)

numeric_vec = c(num1, num2, num3)

Vectors can be easilly combined



In [21]:

    
combined_vec = c(numeric_vec, numeric_vec)
print(combined_vec)









    



[1]  0.000000 -5.000000  3.141593  0.000000 -5.000000  3.141593

Remember hoow vectors can only store one TYPE of variabe? So what would happen if we do this?



In [22]:

    
combined_vec = c(str1, num2)

Well? No ERROR? let's have a look at it



In [23]:

    
combined_vec
class(combined_vec)









    





	'I'
	'-5'








    




'character'

Vector creation

There are many ways how to create vectors. Below are some of the most common one.

Extremely common way to create integer vectors is the following.



In [24]:

    
numeric_vec2 = 1:5
numeric_vec2
numeric_vec3 = -5:-10
numeric_vec3

We can create simple vectors with the rep function



In [25]:

    
all_ones = rep(1, 100)

We can also create sequences with the use of seq function.



In [26]:

    
small_increments = seq(1, 100, by = 0.1)
larger_increments = seq(2, 100, length.out = 50)

If you want to just increment by one, use the column operator.

Another way to create vectors is through logical comparison.



In [27]:

    
1:5 == seq(1,5)









    





	TRUE
	TRUE
	TRUE
	TRUE
	TRUE



In [28]:

    
1:10 > 7









    





	FALSE
	FALSE
	FALSE
	FALSE
	FALSE
	FALSE
	FALSE
	TRUE
	TRUE
	TRUE

We can also do something more fancier, such as random vectors. Will come in handy for sure



In [29]:

    
set.seed(666)
uniform_deviations = runif(25)
uniform_deviations









    





	0.774368490325287
	0.197224191389978
	0.978013844229281
	0.201327350223437
	0.36124442727305
	0.742611942114308
	0.97872843942605
	0.498113709036261
	0.0133158357348293
	0.259946128586307
	0.775893080746755
	0.0163790525402874
	0.0957447842229158
	0.142163540003821
	0.21112623764202
	0.811256443616003
	0.0365471958648413
	0.891637413064018
	0.483236411120743
	0.46666452800855
	0.984224080340937
	0.601345547009259
	0.038344347383827
	0.141495691146702
	0.806385525269434



In [30]:

    
rand1 = sample(c(1:25), 25, rep=F) #cant't repeat
rand1



In [31]:

    
rand2 = sample(c(1:25), 25, rep=T) #can repeat
rand2



In [32]:

    
favourite_games = sample(c("CS Files", "Terra Mystica", "Cosmic Encounter", "Pandemic", "Takenoko"))
favourite_games









    





	'Pandemic'
	'Cosmic Encounter'
	'CS Files'
	'Terra Mystica'
	'Takenoko'

Vector access

vectors (and matrices) are accessed witht the [] sign - [row, column]/[i, j]. First position is the nth element in vector or nth row in matrix, second number is



In [33]:

    
num_vec = 1:5
games_vec = sample(c("CS Files", "Terra Mystica", "Cosmic Encounter", "Pandemic", "Takenoko"))

num_vec[1] * num_vec[2]
games_vec[2]
games_vec[c(1:3)]









    




2






    




'Takenoko'






    





	'Pandemic'
	'Takenoko'
	'CS Files'



In [34]:

    
num_vec = 1:5
games_vec = c("CS Files", "Terra Mystica", "Cosmic Encounter", "Pandemic", "Takenoko")
games_vec[which(num_vec > 4)]









    




'Takenoko'

Another very common way to access vectors is through logical vectors.;



In [35]:

    
logical_vec = rep(c(T, F), 5)
logical_vec
num_vec = 1:10
num_vec
num_vec[logical_vec]









    





	TRUE
	FALSE
	TRUE
	FALSE
	TRUE
	FALSE
	TRUE
	FALSE
	TRUE
	FALSE








    





	1
	2
	3
	4
	5
	6
	7
	8
	9
	10








    





	1
	3
	5
	7
	9

We can also exclude elements from vectors by using - sign



In [36]:

    
game_of_dead_people = c("Jon", "Sansa", "Hodor", "Arya", "Ned", "Bran", "Rickon")
game_of_dead_people[-1]
game_of_dead_people[-c(1:3, 7)]









    





	'Sansa'
	'Hodor'
	'Arya'
	'Ned'
	'Bran'
	'Rickon'








    





	'Arya'
	'Ned'
	'Bran'

Vector subsetting

we can easily subset vectors by numbers, but what if we want to remove Bran from it but don't know which element it is?

We can easily use which function



In [37]:

    
game_of_dead_people = c("Jon", "Sansa", "Hodor", "Arya", "Ned", "Bran", "Rickon")
bran_idx = which(game_of_dead_people == "Bran")
bran_idx
game_of_dead_people[bran_idx]



In [38]:

    
game_of_dead_people = c("Jon", "Sansa", "Hodor", "Arya", "Ned", "Bran", "Rickon")
non_bran_idx = which(game_of_dead_people != "Bran")
non_bran_idx
game_of_dead_people[non_bran_idx]









    





	1
	2
	3
	4
	5
	7








    





	'Jon'
	'Sansa'
	'Hodor'
	'Arya'
	'Ned'
	'Rickon'



In [39]:

    
game_of_dead_people = c("Jon", "Sansa", "Hodor", "Arya", "Ned", "Bran", "Rickon")
cool_dudes = c("Jon", "Arya", "Ned")
cool_idx = which(game_of_dead_people %in% cool_dudes)
uncool_idx = which(!(game_of_dead_people %in% cool_dudes))
game_of_dead_people[cool_idx]
game_of_dead_people[uncool_idx]









    





	'Jon'
	'Arya'
	'Ned'








    





	'Sansa'
	'Hodor'
	'Bran'
	'Rickon'

And the other, more common way, is to use logical vectors. It works very similary, just drops the function which.



In [40]:

    
game_of_dead_people = c("Jon", "Sansa", "Hodor", "Arya", "Ned", "Bran", "Rickon")
bran_idx = game_of_dead_people == "Bran"
bran_idx
game_of_dead_people[bran_idx]









    





	FALSE
	FALSE
	FALSE
	FALSE
	FALSE
	TRUE
	FALSE








    




'Bran'



In [41]:

    
game_of_dead_people = c("Jon", "Sansa", "Hodor", "Arya", "Ned", "Bran", "Rickon")
cool_dudes = c("Jon", "Arya", "Ned")
cool_idx = game_of_dead_people %in% cool_dudes
uncool_idx = !(game_of_dead_people %in% cool_dudes)
cool_idx
uncool_idx
game_of_dead_people[cool_idx]
game_of_dead_people[uncool_idx]









    





	TRUE
	FALSE
	FALSE
	TRUE
	TRUE
	FALSE
	FALSE








    





	FALSE
	TRUE
	TRUE
	FALSE
	FALSE
	TRUE
	TRUE








    





	'Jon'
	'Arya'
	'Ned'








    





	'Sansa'
	'Hodor'
	'Bran'
	'Rickon'

Vector math

You can do easy vector math just like in real life.



In [42]:

    
num_vec1 = 1:5
num_vec2 = -1:-5
num_vec2 + num_vec1



In [44]:

    
years = c(1942,1968,1980,1989:1993, 2000:2005)
years_since_1900 = years - 1900
years_since_1900



In [45]:

    
cm = c(5, 10, 8, 13, 1, 48, 12.5)
inches = cm * 0.393701
inches

Try what happens when you try to do math with unequal length of vectors?

Practice time

Try to solve following problems

Create a vector of our names and then select one "winner" at random.
Create a vector of numbers from 1 to 99 by two (1 3 5 .. 99) and then select three elements at random.
Create a random logical vector of length 50 (T F T F F F T F etc.)
Create a random vector of "Male" "Female" elements of lenght 50
Use set.seed function to create vectors 3 and 4 and use them to select only one gender.