# List exercises

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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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