18.4 Chapter 7: Indexing vectors with []

Table 17.2: Some of my favorite movies

movie	year	boxoffice	genre	time	rating
Whatever Works	2009	35.0	Comedy	92	PG-13
It Follows	2015	15.0	Horror	97	R
Love and Mercy	2015	15.0	Drama	120	R
The Goonies	1985	62.0	Adventure	90	PG
Jiro Dreams of Sushi	2012	3.0	Documentary	81	G
There Will be Blood	2007	10.0	Drama	158	R
Moon	2009	321.0	Science Fiction	97	R
Spice World	1988	79.0	Comedy	-84	PG-13
Serenity	2005	39.0	Science Fiction	119	PG-13
Finding Vivian Maier	2014	1.5	Documentary	84	Unrated

0. Create new data vectors for each column.

movie <- c("Whatever Works", "It Follows", "Love and Mercy", 
             "The Goonies", "Jiro Dreams of Sushi",
             "There Will be Blood", "Moon", 
             "Spice World", "Serenity", "Finding Vivian Maier")

year <- c(2009, 2015, 2015, 1985, 2012, 2007, 2009, 1988, 2005, 2014)

boxoffice <- c(35, 15, 15, 62, 3, 10, 321, 79, 39, 1.5)

genre <- c("Comedy", "Horror", "Drama", "Adventure", "Documentary", 
           "Drama", "Science Fiction", "Comedy", "Science Fiction", 
           "Documentary")

time <- c(92, 97, 120, 90, 81, 158, 97, -84, 119, 84)

rating <- c("PG-13", "R", "R", "PG", "G", "R", "R", 
            "PG-13", "PG-13", "Unrated")

1. What is the name of the 10th movie in the list?

movie[10]
## [1] "Finding Vivian Maier"

2. What are the genres of the first 4 movies?

genre[1:4]
## [1] "Comedy"    "Horror"    "Drama"     "Adventure"

3. Some joker put Spice World in the movie names – it should be ``The Naked Gun’’ Please correct the name.

movie[movie == "Spice World"] <- "The Naked Gun"

4. What were the names of the movies made before 1990?

movie[year < 1990]
## [1] "The Goonies"   "The Naked Gun"

5. How many movies were Dramas? What percent of the 10 movies were Comedies?

sum(genre == "Drama")
## [1] 2

mean(genre == "Comedy")
## [1] 0.2

6. One of the values in the time vector is invalid. Convert any invalid values in this vector to NA. Then, calculate the mean movie time

time[time < 0] <- NA

mean(time, na.rm = TRUE)
## [1] 104

7. What were the names of the Comedy movies? What were their boxoffice totals? (Two separate questions)

movie[genre == "Comedy"]
## [1] "Whatever Works" "The Naked Gun"

boxoffice[genre == "Comedy"]
## [1] 35 79

8. What were the names of the movies that made less than $50 Million dollars AND were Comedies?

movie[boxoffice < 50 & genre == "Comedy"]
## [1] "Whatever Works"

9. What was the median boxoffice revenue of movies rated either G or PG?

median(boxoffice[rating %in% c("G", "PG")])
## [1] 32

# OR

median(boxoffice[rating == "G" | rating == "PG"])
## [1] 32

10. What percent of the movies were either rated R OR were comedies?

mean(rating == "R" | genre == "Comedy")
## [1] 0.6