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**

Zee says

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!

asd says

How can I get answers????

asd says

Oh.. I found it. Thanks.

Antora Das says

I need solution. So, how can I get it?

Han de Vries says

Hi Antora, there’s a link to the solutions at the beginning of each exercise set “Answers to the exercises are available here.” https://www.r-exercises.com/2015/12/31/list-exercises-solutions/

Fabio says

Hi. Thanks a lot for this exciting work