In the exercises below we cover the basics of lists. Before proceeding, first read section 6.1-6.2 of An Introduction to R, and the help pages for the sum, length, strsplit, and setdiff functions.
Answers to the exercises are available here.
Exercise 1
If:
p <- c(2,7,8),
q <- c("A", "B", "C") and
x <- list(p, q),
then what is the value of x[2]?
a. NULL
b. "A" "B" "C"
c. "7"
Exercise 2
If:
w <- c(2, 7, 8)
v <- c("A", "B", "C")
x <- list(w, v),
then which R statement will replace "A" in x with "K".
a. x[[2]] <- "K"
b. x[[2]][1] <- "K"
c. x[[1]][2] <- "K"
Exercise 3
If a <- list ("x"=5, "y"=10, "z"=15), which R statement will give the sum of all elements in a?
a. sum(a)
b. sum(list(a))
c. sum(unlist(a))
Exercise 4
If Newlist <- list(a=1:10, b="Good morning", c="Hi"), write an R statement that will add 1 to each element of the first vector in Newlist.
Exercise 5
If b <- list(a=1:10, c="Hello", d="AA"), write an R expression that will give all elements, except the second, of the first vector of b.
Exercise 6
Let x <- list(a=5:10, c="Hello", d="AA"), write an R statement to add a new item z = "NewItem" to the list x.
Exercise 7
Consider y <- list("a", "b", "c"), write an R statement that will assign new names "one", "two" and "three" to the elements of y.
Exercise 8
If x <- list(y=1:10, t="Hello", f="TT", r=5:20), write an R statement that will give the length of vector r of x.
Exercise 9
Let string <- "Grand Opening", write an R statement to split this string into two and return the following output:
[[1]]
[1] "Grand"
[[2]]
[1] "Opening"
Exercise 10
Let:
y <- list("a", "b", "c") and
q <- list("A", "B", "C", "a", "b", "c").
Write an R statement that will return all elements of q that are not in y, with the following result:
[[1]]
[1] "A"
[[2]]
[1] "B"
[[3]]
[1] "C"
Want some extra practice with lists? Please take a look here
In exercise 5, is there a solution to print ALL elements of the list except the second element of the first item in the list?
The solution shows how to print only the first item of the list without the second item…
Thank you!
How can I get answers????
Oh.. I found it. Thanks.