Data structures

Author

Jeffrey R. Stevens

Published

February 6, 2023

In-class coding

Make a sequence from 0 to 100 in steps of 10.

seq(0, 100, 10)

 [1]   0  10  20  30  40  50  60  70  80  90 100

Create a repetition of “yes” and “no” with 10 instance of each, alternating between the two. Then make one with 10 “yes” and then 10 “no”.

rep(c("yes", "no"), times = 10)

 [1] "yes" "no"  "yes" "no"  "yes" "no"  "yes" "no"  "yes" "no"  "yes" "no" 
[13] "yes" "no"  "yes" "no"  "yes" "no"  "yes" "no"

rep(c("yes", "no"), each = 10)

 [1] "yes" "yes" "yes" "yes" "yes" "yes" "yes" "yes" "yes" "yes" "no"  "no" 
[13] "no"  "no"  "no"  "no"  "no"  "no"  "no"  "no"

Add the argument n = 10 to head(mtcars). What does this do?

head(mtcars, n =  10)

                   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
Datsun 710        22.8   4 108.0  93 3.85 2.320 18.61  1  1    4    1
Hornet 4 Drive    21.4   6 258.0 110 3.08 3.215 19.44  1  0    3    1
Hornet Sportabout 18.7   8 360.0 175 3.15 3.440 17.02  0  0    3    2
Valiant           18.1   6 225.0 105 2.76 3.460 20.22  1  0    3    1
Duster 360        14.3   8 360.0 245 3.21 3.570 15.84  0  0    3    4
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
Merc 280          19.2   6 167.6 123 3.92 3.440 18.30  1  0    4    4

Extra coding practice

Vectors

Create a vector called dog_names with the values Bella, Daisy, and Max.

dog_names <- c("Bella", "Daisy", "Max")

Create a vector called sex with the values Female, Male, and Male.

sex <- c("Female", "Female", "Male")

Use the index operator to print to console only Daisy and Max from dog_names.

dog_names[2:3]

[1] "Daisy" "Max"

Replace the Daisy entry with Luna and print dog_names to console.

dog_names[2] <- "Luna"
dog_names

[1] "Bella" "Luna"  "Max"

Lists

Copy/paste and run this code: (mylist <- list(a = 1:4, b = c(4, 3, 8, 5), c = LETTERS[10:15], d = c("yes", "yes")))

(mylist <- list(a = 1:4, b = c(4, 3, 8, 5), c = LETTERS[10:15], d = c("yes", "yes")))

$a
[1] 1 2 3 4

$b
[1] 4 3 8 5

$c
[1] "J" "K" "L" "M" "N" "O"

$d
[1] "yes" "yes"

Check the data types for each list element individually.

typeof(mylist$a)

[1] "integer"

typeof(mylist$b)

[1] "double"

typeof(mylist$c)

[1] "character"

typeof(mylist$d)

[1] "character"

Check the data types for each list element with one command.

str(mylist)

List of 4
 $ a: int [1:4] 1 2 3 4
 $ b: num [1:4] 4 3 8 5
 $ c: chr [1:6] "J" "K" "L" "M" ...
 $ d: chr [1:2] "yes" "yes"

Combine list elements a and b into a single vector.

c(mylist$a, mylist$b)

[1] 1 2 3 4 4 3 8 5

Data frames

Create a data frame called mydf with three columns: x, y, and z and five rows. For x assign any five numbers, for y assign any five character strings, and for z assign any five logical values.

(mydf <- data.frame(x = sample(1:10, 5, replace = TRUE), y = sample(letters, 5), z = sample(c(TRUE, FALSE), 5, replace = TRUE)))

  x y     z
1 5 l  TRUE
2 3 c  TRUE
3 4 m FALSE
4 4 w  TRUE
5 5 j FALSE

Create a data frame called dogs that combines the dog_names and sex vectors and print to console.

(dogs <- data.frame(dog_names, sex))

  dog_names    sex
1     Bella Female
2      Luna Female
3       Max   Male

Print to console just Luna’s row.

dogs[2, ]

  dog_names    sex
2      Luna Female

Print to console the number of rows in dogs.

nrow(dogs)

[1] 3