--3-Matrices

#1-What's a matrix?

#Construct a matrix with 3 rows containing the numbers 1 up to 9, 
# filled row-wise.
matrix(1:9,byrow=TRUE,nrow=3)

#2-Analyzing matrices

#Use c(new_hope, empire_strikes, return_jedi) to combine-
#the three vectors into one vector. Call this vector box_office.
#Construct a matrix with 3 rows, where each row represents a movie. 
#Use the matrix() function to this. 
#The first argument is the vector box_office, containing 
#all box office figures. 
#Next, you'll have to specify nrow = 3 and byrow = TRUE. 
#Name the resulting matrix star_wars_matrix.

# Box office Star Wars (in millions!)
  new_hope <-c( 460.998 , 314.4 )
  empire_strikes <- c(290.475, 247.900)
  return_jedi <- c(309.306, 165.8)
  
# Create box_office
  box_office <-c(new_hope,empire_strikes,return_jedi) 
  
# Construct star_wars_matrix
  star_wars_matrix <- matrix(box_office,byrow=TRUE,nrow=3)
  star_wars_matrix

#3-Naming a matrix

#Use colnames() to name the columns of star_wars_matrix with 
#the region vector.
#Use rownames() to name the rows of star_wars_matrix with the 
#titles vector.
#Print out star_wars_matrix to see the result of your work.
    
# Box office Star Wars (in millions!)
  new_hope <- c(460.998, 314.4)
  empire_strikes <- c(290.475, 247.900)
  return_jedi <- c(309.306, 165.8)
  
  # Construct matrix
  star_wars_matrix <- matrix(c(new_hope, empire_strikes, return_jedi), 
  nrow = 3, byrow = TRUE)
  
  # Vectors region and titles, used for naming
  region <- c("US", "non-US")
  titles <- c("A New Hope", "The Empire Strikes Back", 
  "Return of the Jedi")
  
  # Name the columns with region
  colnames(star_wars_matrix)<-region
  
  # Name the rows with titles
  rownames(star_wars_matrix)<-titles
  
  # Print out star_wars_matrix
  star_wars_matrix

#4-Calculating the worldwide box office

#Calculate the worldwide box office figures for 
#the three movies and put these in the vector named worldwide_vector.

 # Construct star_wars_matrix
  box_office <-c(460.998, 314.4, 290.475, 247.900, 309.306, 165.8)
  star_wars_matrix <- matrix(box_office, nrow = 3, byrow = TRUE,
  dimnames = list(c("A New Hope", "The Empire Strikes Back", 
  "Return of the Jedi"), 
  c("US", "non-US")))
  
 star_wars_matrix
  
  # Calculate worldwide box office figures
  worldwide_vector <- rowSums(star_wars_matrix)
  worldwide_vector

#5-Adding a column for the Worldwide box office

#Add worldwide_vector as a new column to the star_wars_matrix and 
#assign the result to all_wars_matrix. 
#Use the cbind() function.

# Construct star_wars_matrix
  box_office <- c(460.998, 314.4, 290.475, 247.900, 309.306, 165.8)
  star_wars_matrix <- matrix(box_office, nrow = 3, byrow = TRUE,
  dimnames = list(c("A New Hope", "The Empire Strikes Back", 
  "Return of the Jedi"), 
  c("US", "non-US")))
  
  star_wars_matrix
  
  # The worldwide box office figures
  worldwide_vector <- rowSums(star_wars_matrix)
  worldwide_vector
  
  # Bind the new variable worldwide_vector as a column to 
  #star_wars_matrix
  all_wars_matrix <- cbind(star_wars_matrix,worldwide_vector)
  all_wars_matrix

#6-Adding a row

#Use rbind() to paste together star_wars_matrix and star_wars_matrix2, 
#in this order. 
#Assign the resulting matrix to all_wars_matrix. 

# Construct star_wars_matrix1
    box_office <- c(460.998, 314.4, 290.475, 247.900, 309.306, 165.8)
    star_wars_matrix <- matrix(box_office, nrow = 3, byrow = TRUE,
    dimnames = list(c("A New Hope", "The Empire Strikes Back", 
    "Return of the Jedi")
    , 
    c("US", "non-US")))
    star_wars_matrix
    
# Construct star_wars_matrix2
box_office2 <- c( 474.5,  552.5,  552.5,  338.7, 380.3, 468.5)
star_wars_matrix2 <- matrix(box_office2, nrow = 3, byrow = TRUE,
dimnames = list(c("The Phantom Menace", "Attack of the Clones", 
"Revenge of the Sith")
, c("US", "non-US")))
 
star_wars_matrix2
    
    
  # star_wars_matrix and star_wars_matrix2 are available in 
  #your workspace
  star_wars_matrix  
  star_wars_matrix2 
  
  # Combine both Star Wars trilogies in one matrix
  all_wars_matrix <- rbind(star_wars_matrix,star_wars_matrix2)
  all_wars_matrix

#7-The total box office revenue for the entire saga

# Construct star_wars_matrix1
box_office <- c(460.998, 314.4, 290.475, 247.900, 309.306, 165.8)
star_wars_matrix <- matrix(box_office, nrow = 3, byrow = TRUE,
dimnames = list(c("A New Hope", "The Empire Strikes Back", 
"Return of the Jedi")
, 
c("US", "non-US")))
star_wars_matrix
    
# Construct star_wars_matrix2
box_office2 <- c( 474.5,  552.5,  552.5,  338.7, 380.3, 468.5)
star_wars_matrix2 <- matrix(box_office2, nrow = 3, byrow = TRUE,
dimnames = list(c("The Phantom Menace", "Attack of the Clones", 
"Revenge of the Sith")
, 
 c("US", "non-US")))
 
star_wars_matrix2
    
  # star_wars_matrix and star_wars_matrix2 are available in 
  #your workspace
  star_wars_matrix  
  star_wars_matrix2 
  
  # Combine both Star Wars trilogies in one matrix
  all_wars_matrix <- rbind(star_wars_matrix,star_wars_matrix2)
  all_wars_matrix

  # Total revenue for US and non-US
  total_revenue_vector <- colSums(all_wars_matrix)
  
  # Print out total_revenue_vector
  total_revenue_vector

#8-Selection of matrix elements

# Construct star_wars_matrix1
    box_office <- c(460.998, 314.4, 290.475, 247.900, 309.306, 165.8)
    star_wars_matrix <- matrix(box_office, nrow = 3, byrow = TRUE,
    dimnames = list(c("A New Hope", "The Empire Strikes Back", 
    "Return of the Jedi")
    , 
    c("US", "non-US")))
    star_wars_matrix
    
# Construct star_wars_matrix2
box_office2 <- c( 474.5,  552.5,  552.5,  338.7, 380.3, 468.5)
star_wars_matrix2 <- matrix(box_office2, nrow = 3, byrow = TRUE,
dimnames = list(c("The Phantom Menace", "Attack of the Clones", 
"Revenge of the Sith")
, 
 c("US", "non-US")))
 
star_wars_matrix2
    
  # star_wars_matrix and star_wars_matrix2 are available in 
  #your workspace
  star_wars_matrix  
  star_wars_matrix2 
  
  # Combine both Star Wars trilogies in one matrix
  all_wars_matrix <- rbind(star_wars_matrix,star_wars_matrix2)
  all_wars_matrix
  
  # Select the non-US revenue for all movies
  non_us_all <- all_wars_matrix[,2]
  
  # Average non-US revenue
  mean(non_us_all)
  
  # Select the non-US revenue for first two movies
  non_us_some <- all_wars_matrix[1:2,2]
  
  # Average non-US revenue for first two movies
  mean(non_us_some)

#9-A little arithmetic with matrices

# Construct star_wars_matrix1
    box_office <- c(460.998, 314.4, 290.475, 247.900, 309.306, 165.8)
    star_wars_matrix <- matrix(box_office, nrow = 3, byrow = TRUE,
    dimnames = list(c("A New Hope", "The Empire Strikes Back", 
    "Return of the Jedi")
    , 
    c("US", "non-US")))
    star_wars_matrix
    
# Construct star_wars_matrix2
box_office2 <- c( 474.5,  552.5,  552.5,  338.7, 380.3, 468.5)
star_wars_matrix2 <- matrix(box_office2, nrow = 3, byrow = TRUE,
dimnames = list(c("The Phantom Menace", "Attack of the Clones", 
"Revenge of the Sith")
, 
 c("US", "non-US")))
 
star_wars_matrix2
  
  # star_wars_matrix and star_wars_matrix2 are available in your workspace
  star_wars_matrix  
  star_wars_matrix2 
  
  # Combine both Star Wars trilogies in one matrix
  all_wars_matrix <- rbind(star_wars_matrix,star_wars_matrix2)
  all_wars_matrix
  
  # Estimate the visitors
  visitors <- all_wars_matrix/5
  
  # Print the estimate to the console
  visitors

#10- A little arithmetic with matrices (2)

# Construct star_wars_matrix1
    box_office <- c(460.998, 314.4, 290.475, 247.900, 309.306, 165.8)
    star_wars_matrix <- matrix(box_office, nrow = 3, byrow = TRUE,
    dimnames = list(c("A New Hope", "The Empire Strikes Back", 
    "Return of the Jedi")
    , 
    c("US", "non-US")))
    star_wars_matrix
    
# Construct star_wars_matrix2
box_office2 <- c( 474.5,  552.5,  552.5,  338.7, 380.3, 468.5)
star_wars_matrix2 <- matrix(box_office2, nrow = 3, byrow = TRUE,
dimnames = list(c("The Phantom Menace", "Attack of the Clones", 
"Revenge of the Sith")
, 
 c("US", "non-US")))
 
star_wars_matrix2
  
  # star_wars_matrix and star_wars_matrix2 are available in 
  #your workspace
  star_wars_matrix  
  star_wars_matrix2 
  
  # Combine both Star Wars trilogies in one matrix
  all_wars_matrix <- rbind(star_wars_matrix,star_wars_matrix2)
  all_wars_matrix

# create ticket_prices_matrix
box_office <- c(5,5, 6,6, 7,7)
ticket_prices_matrix1 <- matrix(box_office, nrow = 3, byrow = TRUE,
dimnames = list(c("A New Hope", "The Empire Strikes Back", 
"Return of the Jedi"), 
c("US", "non-US")))

# Construct ticket_prices_matrix2
box_office2 <- c(4,4, 4.5,4.5, 4.9,4.9)
ticket_prices_matrix2<- matrix(box_office2, nrow = 3, byrow = TRUE,
dimnames = list(c("The Phantom Menace", "Attack of the Clones", 
"Revenge of the Sith")
, 
c("US", "non-US")))
ticket_prices_matrix<-rbind(ticket_prices_matrix1,ticket_prices_matrix2)

# Estimated number of visitors
visitors <- all_wars_matrix/ticket_prices_matrix

# US visitors
us_visitors <- visitors[,1]

# Average number of US visitors
mean(us_visitors)