Exercise 1:
Create a data frame named students with the following columns, Name, Age, Grade,
and Subject. Populate it with atleast 5 rows of sample data.
students <- data.frame(
Name = c("Alice","Bob","Lukman","Aishah","Kamal"),
Age = c(10,20,19,28,21),
Grade = as.factor(c("A","A","B","A","C")),
Subject = as.factor(c("Math","History","Math","English","History"))
)
students Name Age Grade Subject
1 Alice 10 A Math
2 Bob 20 A History
3 Lukman 19 B Math
4 Aishah 28 A English
5 Kamal 21 C HistoryDisplay the structure of the students data frame using the str() function.
str(students)'data.frame': 5 obs. of 4 variables:
$ Name : chr "Alice" "Bob" "Lukman" "Aishah" ...
$ Age : num 10 20 19 28 21
$ Grade : Factor w/ 3 levels "A","B","C": 1 1 2 1 3
$ Subject: Factor w/ 3 levels "English","History",..: 3 2 3 1 2Add a new column to the students data frame named Attendance and populate
it with sample data.
students$Attendance <- c("Present", "Absent", "Present", "Present", "Absent")
students Name Age Grade Subject Attendance
1 Alice 10 A Math Present
2 Bob 20 A History Absent
3 Lukman 19 B Math Present
4 Aishah 28 A English Present
5 Kamal 21 C History AbsentExercise 2:
From the mtcars dataset, extract the mpg(miles per gallon) and hp (horsepower)
columns and save them as a new data frame named car_specs.
car_specs <- mtcars[ , c("mpg","hp")]Retrieve the first 6 rows of the car_specs data frame.
head(car_specs) mpg hp
Mazda RX4 21.0 110
Mazda RX4 Wag 21.0 110
Datsun 710 22.8 93
Hornet 4 Drive 21.4 110
Hornet Sportabout 18.7 175
Valiant 18.1 105Create a subset of mtcars containing only cars with 6 cylinders (cyl).
six_cyl_cars <- mtcars[mtcars$cyl == 6, ]
six_cyl_cars mpg cyl disp hp drat wt qsec vs am gear carb
Mazda RX4 21.0 6 160.0 110 3.90 2.620 16.46 0 1 4 4
Mazda RX4 Wag 21.0 6 160.0 110 3.90 2.875 17.02 0 1 4 4
Hornet 4 Drive 21.4 6 258.0 110 3.08 3.215 19.44 1 0 3 1
Valiant 18.1 6 225.0 105 2.76 3.460 20.22 1 0 3 1
Merc 280 19.2 6 167.6 123 3.92 3.440 18.30 1 0 4 4
Merc 280C 17.8 6 167.6 123 3.92 3.440 18.90 1 0 4 4
Ferrari Dino 19.7 6 145.0 175 3.62 2.770 15.50 0 1 5 6Exercise 3:
Calculate the median horsepower (hp) of all cars in the mtcars dataset
median(mtcars$hp)[1] 123How many cars in the dataset have an automatic transmission (am coumn: 0 represent
automatic, 1 represents manual)?
nrow(mtcars[mtcars$am == 0, ])[1] 19Which car model in the mtcars dataset has the highest miles per gallon (mpg)?
rownames(mtcars)[which.max(mtcars$mpg)][1] "Toyota Corolla"Exercise 4:
Extract and display all cars from mtcars with 4 cylinders (cyl).
rownames(mtcars[mtcars$cyl == 4, ]) [1] "Datsun 710" "Merc 240D" "Merc 230" "Fiat 128"
[5] "Honda Civic" "Toyota Corolla" "Toyota Corona" "Fiat X1-9"
[9] "Porsche 914-2" "Lotus Europa" "Volvo 142E" How many cars in the mtcars dataset have more than 100 horsepower (hp) and
weight (column wt) less than 3,000 lbs?
nrow(mtcars[mtcars$hp > 100 & mtcars$wt < 3, ])[1] 5Retrieve all car models from mtcars that have an automatic transmission and can
cover more than 20 miles per gallon.
rownames(mtcars[mtcars$am == 0 & mtcars$mpg > 20, ])[1] "Hornet 4 Drive" "Merc 240D" "Merc 230" "Toyota Corona" Exercise 5:
How many rows and columns are present in the mtcars dataset?
dim(mtcars)[1] 32 11What are names all of all the columns in the dataset?
colnames(mtcars) [1] "mpg" "cyl" "disp" "hp" "drat" "wt" "qsec" "vs" "am" "gear"
[11] "carb"Display the last 8 rows of the dataset.
tail(mtcars, 8) mpg cyl disp hp drat wt qsec vs am gear carb
Pontiac Firebird 19.2 8 400.0 175 3.08 3.845 17.05 0 0 3 2
Fiat X1-9 27.3 4 79.0 66 4.08 1.935 18.90 1 1 4 1
Porsche 914-2 26.0 4 120.3 91 4.43 2.140 16.70 0 1 5 2
Lotus Europa 30.4 4 95.1 113 3.77 1.513 16.90 1 1 5 2
Ford Pantera L 15.8 8 351.0 264 4.22 3.170 14.50 0 1 5 4
Ferrari Dino 19.7 6 145.0 175 3.62 2.770 15.50 0 1 5 6
Maserati Bora 15.0 8 301.0 335 3.54 3.570 14.60 0 1 5 8
Volvo 142E 21.4 4 121.0 109 4.11 2.780 18.60 1 1 4 2Exercise 6:
Calculate the median horsepower (hp) of all cars in the dataset.
median(mtcars$hp)[1] 123How many cars in the dataset have an automatic transmission (am column: 0 represents
automatic, 1 represents manual)?
sum(mtcars$am == 0)[1] 19Which car model has the highest miles per gallon (mpg)?
rownames(mtcars)[which.max(mtcars$mpg)][1] "Toyota Corolla"Exercise 7:
Extract and display all cars with 4 cylinders (cyl).
mtcars[mtcars$cyl == 4, ] mpg cyl disp hp drat wt qsec vs am gear carb
Datsun 710 22.8 4 108.0 93 3.85 2.320 18.61 1 1 4 1
Merc 240D 24.4 4 146.7 62 3.69 3.190 20.00 1 0 4 2
Merc 230 22.8 4 140.8 95 3.92 3.150 22.90 1 0 4 2
Fiat 128 32.4 4 78.7 66 4.08 2.200 19.47 1 1 4 1
Honda Civic 30.4 4 75.7 52 4.93 1.615 18.52 1 1 4 2
Toyota Corolla 33.9 4 71.1 65 4.22 1.835 19.90 1 1 4 1
Toyota Corona 21.5 4 120.1 97 3.70 2.465 20.01 1 0 3 1
Fiat X1-9 27.3 4 79.0 66 4.08 1.935 18.90 1 1 4 1
Porsche 914-2 26.0 4 120.3 91 4.43 2.140 16.70 0 1 5 2
Lotus Europa 30.4 4 95.1 113 3.77 1.513 16.90 1 1 5 2
Volvo 142E 21.4 4 121.0 109 4.11 2.780 18.60 1 1 4 2How many cars have more than 100 horsepower (hp) and weight (column wt) less than
3,000 lbs?
sum(mtcars$hp > 100 & mtcars$wt < 3)[1] 5Retrieve all car models that have an automatic transmission and can cover more than 20 miles
per gallon.
rownames(mtcars[mtcars$am == 0 & mtcars$mpg > 20, ])[1] "Hornet 4 Drive" "Merc 240D" "Merc 230" "Toyota Corona"