Reviewing

# a random vector containing 1, 3, 4, 6, 9
random <- c(1, 3, 4, 6, 9)
random
## [1] 1 3 4 6 9

Insert new value to the random vector: 2 and 10

# R can overwrite
random <- c(random, 2, 10)
random
## [1]  1  3  4  6  9  2 10

R OVERWRITES!!!!!!

SOME FUNCTIONS

length() - check for the number of components within a variable.

# check for the number of components within vector random. 
length(random)
## [1] 7

sum() - take the sum of all of the components/value within that vector.

# find the sum of ALL values within random.
# 1 + 3 + 4 + 6 + 9 + 2 + 10 
1 + 3 + 4 + 6 + 9 + 2 + 10 
## [1] 35
sum(random)
## [1] 35
# square EACH component within the vector
random^2
## [1]   1   9  16  36  81   4 100
# sum of the squared number 
sum(random^2)
## [1] 247
# random2 containing 3, 2, 5, 1, 3, 4 , 8
random2 <- c(3, 2, 5, 1, 3, 4, 8)
random2
## [1] 3 2 5 1 3 4 8
random + random2
## [1]  4  5  9  7 12  6 18

Valid variable name.

  1. Contain only letters, numbers, dots (.), and underscore (_).
  2. Can start with letters OR dots NOT followed by a number.

var_name2. VALID

var_name% INVALID

2var_name INVALID

var name INVALID

var.name VALID

.2var_name INVALID

_var_name INVALID

Some more function

rep() -replicate a value/vector

VECTORWISE REP:   rep( vector/value  , #time-repeated )  

COMPONENT WISE REP:   rep( vector/value   , each= )
# fruit containing lemon, strawberry, peach.    
fruit <- c("lemon", "strawberry", "peach")
fruit
## [1] "lemon"      "strawberry" "peach"
# repeat vector fruit 3 times  (vector wise)
rep(fruit, 3)
## [1] "lemon"      "strawberry" "peach"      "lemon"      "strawberry"
## [6] "peach"      "lemon"      "strawberry" "peach"
# repeat vector fruit component-wise 3 times  
rep(fruit, each=3)
## [1] "lemon"      "lemon"      "lemon"      "strawberry" "strawberry"
## [6] "strawberry" "peach"      "peach"      "peach"

sort() - sort numeric number in order.

ASCENDING/INCREASING sort( vector , decreasing = FALSE )

    decreasing = FALSE is default --> so we can ignore it if we sort increasing.

DESCENDING/DECREASING sort( vector , decreasing = TRUE )

# sort random from small - larger value (Ascending) 
random <- sort(random)  
random
## [1]  1  2  3  4  6  9 10
# sort random2 from large to small (Descending) 
sort(random2, decreasing= T)
## [1] 8 5 4 3 3 2 1

mean() - find mean for the set of score

mean(random2)
## [1] 3.714286

round() - round to a specified decimal places.

round(  value  , #places  )
# round 7.123456 to 2 decimal places
round( 7.123456 , 2)   
## [1] 7.12
# round the result of the mean for random2 to 1 decimal place   
round( mean(random2) , 1  )
## [1] 3.7

unique() - display the unique value within a vector.

unique(random2)   
## [1] 3 2 5 1 4 8
# gender: F, F, M , F, M, M, M,F, F ,F  
gender <- c("F", "F", "M" , "F", "M", "M", "M", "F", "F" ,"F")
gender
##  [1] "F" "F" "M" "F" "M" "M" "M" "F" "F" "F"
length(gender)
## [1] 10
unique(gender)
## [1] "F" "M"
typeof(gender)
## [1] "character"

FACTOR

Factor - is a QUALITIVE vector, meaning that it caries CATEGORICAL values. In other words, factor is a special case of vector where we want to specify that the values within it DO NOT have mathematical meaning.

For eg.: gender, fruit.

factor() - QUALITATIVE + UNranked vector.

  factor(  vector  , labels = c( "name1" , "name2" , ... )  )

as.factor() - - QUALITATIVE + UNranked vector.

ordered() - QUALITATIVE + RANKED vector.

Example: A waitress records her drink order as a set of value : 3, 4, 2, 2, 3, 4, 4, 2, 4, 3, 4, 2.
Based on the price of each type of drink: 2 is for lemonade, 3 is for Sprite, 4 is for Redbull.

# generating vector `drink` containing the raw data.  
drink <- c(3, 4, 2, 2, 3, 4, 4, 2, 4, 3, 4, 2)

# factor `drink`
drink <- factor(drink) 

# labeling the factor 
drink <- factor(drink, labels = c("Lemon" , "Sprite" , "Redbull" ) )
drink
##  [1] Sprite  Redbull Lemon   Lemon   Sprite  Redbull Redbull Lemon   Redbull
## [10] Sprite  Redbull Lemon  
## Levels: Lemon Sprite Redbull

str() - structure of the object.

str(drink)
##  Factor w/ 3 levels "Lemon","Sprite",..: 2 3 1 1 2 3 3 1 3 2 ...

Ranking drinks based on price.

# generating vector `Drink` containing the raw data.  
Drink <- c(3, 4, 2, 2, 3, 4, 4, 2, 4, 3, 4, 2)  

# convert the vector to a ranked factor
Drink <- ordered(Drink)  

# labeling the levels
Drink <- ordered(Drink, labels = c("Lemon" , "Sprite" , "Redbull" ))
Drink 
##  [1] Sprite  Redbull Lemon   Lemon   Sprite  Redbull Redbull Lemon   Redbull
## [10] Sprite  Redbull Lemon  
## Levels: Lemon < Sprite < Redbull
# checking on structure
str(Drink)
##  Ord.factor w/ 3 levels "Lemon"<"Sprite"<..: 2 3 1 1 2 3 3 1 3 2 ...