# List exercises

December 31, 2015
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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"

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