Is it true that this is a vector?

matrix(1)

No,

because `matrix(1)` is two-dimensional.

Is it true that this is a vector?

[,1] [1,] 1

No,

because this is the result of `matrix(1)` and `matrix(1)` is two-dimensional.

How many dimensions does `m` have when `m` is

matrix(1,1)

two

because `m` is a matrix.

How many dimensions does `m` have when `m` is

matrix(1,2)

two

because `m` is a matrix.

How many dimensions does `m` have when `m` is

matrix(1,2,3)

two

because `m` is a matrix.

How many rows does `m` have when `m` is

matrix(1,2,3)

two

because the second argument in `m` is `2`.

How many columns does `m` have when `m` is

matrix(1,2,3)

three

because the third argument in `m` is `3`.

What is `dim(m)` when `m` is

matrix(1,2,3)

`2 3`

because `dim()` is the same as asking the values of the dimensions of a matrix.

How many values does `m` have when `m` is

matrix(1,2,3)

six

because two rows times three columns is six.

What is `sum(m)` where `m` is

matrix(1,2,3)

six

because there are six values in `m` and each value is equal to one.

What is `sum(m)` where `m` is

matrix(2,2,3)

twelve

because there are six values in `m` and each value is equal to two.

What is `length(m)` where `m` is

matrix(2,2,3)

six

because there are six values in `m`.

How many columns does `m` have where `m` is

matrix(15,1,15)

and

dim(m) <- c(3,5)

`5`

because `m` was altered to have five columns by `dim`.

How many columns does `m` have where `m` is

matrix(20,4,5)

and

dim(m) <- c(2,20)

`5`

because the `m` is 20, but the number of values produced by `dim(m) <- c(2,20)` is 40.

What is `m[1,3]` where `m` is

matrix(c(1,2,3),3,3)

`1`

because `matrix(c(1,2,3),3,3)` is

[,1] [,2] [,3] [1,] 1 1 1 [2,] 2 2 2 [3,] 3 3 3

and the value in the first row, third column is `1`.

What is `m[1,3]` where `m` is

matrix(c(1,2,3),2,3)

`2`

because `matrix(c(1,2,3),2,3)` is

[,1] [,2] [,3] [1,] 1 3 2 [2,] 2 1 3

and the value in the first row, third column is `2`.

What is the name of the second column of `m` when `m` is

matrix(c(1,2,3),3,3)

and

colnames(m) <- c("April", "May", "June")

`"May"`

because `"May"` is the second value given to `colnames`.

What is `m[1,3]` where `m` is

matrix(1:6,2,3)

5

because `matrix(1:6,2,3)` is

[,1] [,2] [,3] [1,] 1 3 5 [2,] 2 4 6

and the value in the first row, third column is `5`.

What is `m[1,3]` where `m` is

matrix(1:6,3,3)

`1`

because `matrix(1:6,3,3)` is

[,1] [,2] [,3] [1,] 1 4 1 [2,] 2 5 2 [3,] 3 6 3

and the value in the first row, third column is `1`.

What is `m[1,2]` where `m` is

c(1,2,3,4)

and

dim(m) <- c(2,2)

3

because `m` is now

[,1] [,2] [1,] 1 3 [2,] 2 4

and the value in the first row, second column is `3`.

What is `class(m[1,2])` where `m` is

c(1,2,3,4)

and

dim(m) <- c(2,2)

integer

because the matrix was made out of an integer vector.

What is `m[2,2]` where `m` is

list(1,"2",3,"4")

and

dim(m) <- c(2,2)

[[1]] [1] "4"

because `m` is now

[,1] [,2] [1,] 1 3 [2,] "2" "4"

What is `class(m[2,2])` where `m` is

list(1,"2",3,"4")

and

dim(m) <- c(2,2)

`list`

because the matrix was made out of a list.