Data Structures

#Arrays and Matrices

movie_vector <- c(“akira”, “toy story”, “room”, “wildfire”, “wave”, “wonderland”, “ring”, “wars”, “knight”, “jumanji”)
movie_array <- array(movie_vector, dim = c(4,3))   #dim -> (rows,column)
movie_array[1,2] #accessing (like matrices)
#Unlike array, a matrix must be 2-dimensional
movie_matrix <- matrix(movie_vector, nrow = 3, ncol = 3, byrow = TRUE)
#matrix is arranged in columns by default

#Lists

movie <- list(“toy story”, 1995, c(“Animation”, “Adventure”, “Comedy”))
movie[2:3]

#Named List

movie <- list( name = “toy story”, year = 1995, genre = c(“Animation”, “Adventure”, “Comedy”))
movie$genre

#Adding items
movie[“age”] <- 5 #new element is added at the end

#Remove item
movie[“age”] <- NULL

#Data Frames

#A data frame is a type of structure that contains correlated information.

movies <- data.frame( name = c(“Breakfast Club”, “American Beauty”,  “Black Swan”, “Chicago”),
    year = <- c(1985, 1990, 2010, 2002) )

#access variables using $ symbol
movies$name

#access by specifying column
movies[1]

#access by specifying individual elements
movies[1,2]  #[row , col]

#getting info about structure of data frame
str(movies)

#head and tail
head(movies) #shows first 6 elements of data frame
tail(movies) #shows last 6 elements of data frame

#Inserting a new column
#Specify the new column’s name & assign it to a vector
movies[ “length” ] <- c(81, 140, 135, 119)

#Inserting a new row
movies <- rbind(movies, c(name = “Dr. who”, year = 1964, length = 120) )

#Similarly as an alternate, use cbind() to add a new column

#Deleting a row
movies <- movies[-9,]

#Deleting a column
movies[“length”] <- NULL