3. Matrices

arrNumber <- matrix(c(6, 8, 9, 16, 18, 19, 27, 36, 45, 54, 63, 72), nrow = 3, ncol = 4)
arrNumber

##      [,1] [,2] [,3] [,4]
## [1,]    6   16   27   54
## [2,]    8   18   36   63
## [3,]    9   19   45   72

arrFoods <- matrix(c('Fish', 'Meat', 'Chicken', 'Cheese', 'Milk', 'Butter', 'Eggs', 'Vegetables', 'Fruit', 'Rice', 'Bread', 'Steak'), nrow = 3, ncol = 4)
arrFoods

##      [,1]      [,2]     [,3]         [,4]   
## [1,] "Fish"    "Cheese" "Eggs"       "Rice" 
## [2,] "Meat"    "Milk"   "Vegetables" "Bread"
## [3,] "Chicken" "Butter" "Fruit"      "Steak"

#Number of rows and columns
dim(arrFoods)

## [1] 3 4

#Matrix length
length(arrFoods)

## [1] 12

#Check if an item exists
if("Chicken" %in% arrFoods){
  print("TRUE")
}else{
  print("FALSE")
}

## [1] "TRUE"

#Access matrix items

arrFoods[1,2]

## [1] "Cheese"

arrFoods[, 3]

## [1] "Eggs"       "Vegetables" "Fruit"

arrFoods[3, ]

## [1] "Chicken" "Butter"  "Fruit"   "Steak"

arrFoods[, -3]

##      [,1]      [,2]     [,3]   
## [1,] "Fish"    "Cheese" "Rice" 
## [2,] "Meat"    "Milk"   "Bread"
## [3,] "Chicken" "Butter" "Steak"

#Add rows and columns

c_arrFoods <-  cbind(arrFoods, c('Lemons', 'Plums', 'Papayas'))
c_arrFoods

##      [,1]      [,2]     [,3]         [,4]    [,5]     
## [1,] "Fish"    "Cheese" "Eggs"       "Rice"  "Lemons" 
## [2,] "Meat"    "Milk"   "Vegetables" "Bread" "Plums"  
## [3,] "Chicken" "Butter" "Fruit"      "Steak" "Papayas"

arrFoods <- matrix(c('Fish', 'Meat', 'Chicken', 'Cheese', 'Milk', 'Butter', 'Eggs', 'Vegetables', 'Fruit', 'Rice', 'Bread', 'Steak'), nrow = 3, ncol = 4)
r_arrFoods <- rbind(arrFoods, c('Coconuts', 'Mangoes', 'Pears','Bananas'))
r_arrFoods

##      [,1]       [,2]      [,3]         [,4]     
## [1,] "Fish"     "Cheese"  "Eggs"       "Rice"   
## [2,] "Meat"     "Milk"    "Vegetables" "Bread"  
## [3,] "Chicken"  "Butter"  "Fruit"      "Steak"  
## [4,] "Coconuts" "Mangoes" "Pears"      "Bananas"

#remove rows and columns
arrFoods <- matrix(c('Fish', 'Meat', 'Chicken', 'Cheese', 'Milk', 'Butter', 'Eggs', 'Vegetables', 'Fruit', 'Rice', 'Bread', 'Steak'), nrow = 3, ncol = 4)

arrFoods

##      [,1]      [,2]     [,3]         [,4]   
## [1,] "Fish"    "Cheese" "Eggs"       "Rice" 
## [2,] "Meat"    "Milk"   "Vegetables" "Bread"
## [3,] "Chicken" "Butter" "Fruit"      "Steak"

remove_arrFoods <- arrFoods[-c(1), -c(1)]
remove_arrFoods

##      [,1]     [,2]         [,3]   
## [1,] "Milk"   "Vegetables" "Bread"
## [2,] "Butter" "Fruit"      "Steak"

#Loop through a Matrix

i <- 0
for(rows in 1:nrow(arrFoods)){
  for(columns in 1:ncol(arrFoods)){
    i = i + 1
    cat(i, ". ", arrFoods[rows, columns], "\n", sep = "")
  }
}

## 1. Fish
## 2. Cheese
## 3. Eggs
## 4. Rice
## 5. Meat
## 6. Milk
## 7. Vegetables
## 8. Bread
## 9. Chicken
## 10. Butter
## 11. Fruit
## 12. Steak

arrFoods

##      [,1]      [,2]     [,3]         [,4]   
## [1,] "Fish"    "Cheese" "Eggs"       "Rice" 
## [2,] "Meat"    "Milk"   "Vegetables" "Bread"
## [3,] "Chicken" "Butter" "Fruit"      "Steak"

arrNumber

##      [,1] [,2] [,3] [,4]
## [1,]    6   16   27   54
## [2,]    8   18   36   63
## [3,]    9   19   45   72

#Adding it as a rows
arr_combined_rows <- rbind(arrFoods, arrNumber)
arr_combined_rows

##      [,1]      [,2]     [,3]         [,4]   
## [1,] "Fish"    "Cheese" "Eggs"       "Rice" 
## [2,] "Meat"    "Milk"   "Vegetables" "Bread"
## [3,] "Chicken" "Butter" "Fruit"      "Steak"
## [4,] "6"       "16"     "27"         "54"   
## [5,] "8"       "18"     "36"         "63"   
## [6,] "9"       "19"     "45"         "72"

#Adding it as a columns
arr_combined_columns <- cbind(arrFoods, arrNumber)
arr_combined_columns

##      [,1]      [,2]     [,3]         [,4]    [,5] [,6] [,7] [,8]
## [1,] "Fish"    "Cheese" "Eggs"       "Rice"  "6"  "16" "27" "54"
## [2,] "Meat"    "Milk"   "Vegetables" "Bread" "8"  "18" "36" "63"
## [3,] "Chicken" "Butter" "Fruit"      "Steak" "9"  "19" "45" "72"