Is it true that this is a factor?

factor(c(1,2,3,4,5,6,7,8))

Yes

because it is a vector of eight values passed as an argument to the function `factor`.

Is it true that this is a factor?

factor(1,2,3,4,5,6,7,8)

No

because it is eight values passed as eight arguments to the function `factor`.

How many levels are in factor `f` where

f <- factor(c(1,1,2,1,3,4,3,5,1))

Five

because there are five unique values in factor `f`.

What is `levels(f)` where

f <- factor(c(1,1,2,1,3,4,3,5,1))

[1] "1" "2" "3" "4" "5"

because `levels()` gets a list of factors.

What is `levels(f)` where

f <- factor(c(1,3,4,4), levels=c(1,2,3,4))

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

because a factor can have levels not represented in the data.

What is `f` where

f <- factor(c(1,3,4,4,5), levels=c(1,2,3,4))

[1] 1 3 4 4 <NA>

because a factor cannot have data not represented in the levels.

What is `f` where

f <- factor(c("sunny", "cloudy", "rainy", "cloudy"), levels=c("sunny", "cloudy", "windy", "rainy"))

[1] 1 3 4 4 <NA>

because a factor cannot have data not represented in the levels.

How many levels does `f` have where `f` is

f <- factor(1:6)

six

because `1:6` produces a vector of values `1` through `6`.

How many levels does `f` have where `f` is

f <- factor(1:6,1:9)

nine

because the second argument to `factor()` is `levels` and `1:9` produces a vector of values `1` through `9`.

Is it true that this is an array?

array(1:8, dim=c(8))

yes

because it is a collection of values with one dimension.

Is it true that this is an array?

array(1:8, dim=c(2,4))

yes

because it is a collection of values with two dimensions.

What is `class(a)` where

a <- array(1:8, dim=c(2,4))

matrix

because R treats two-dimensional arrays and matrices the same, and uses matrix to refer to both.

Is it true that this is an array?

array(1:8, dim=c(2,2,2))

yes

because it is a collection of values with three dimensions.

Is it true that this is an array?

array(1:3, dim=c(2,4,2))

yes

because the data used will be recycled to fit the dimensions.

Is it true that this is an array?

array(1:6, dim=c(2,2,2), dimnames=c("rows","columns","groups")

no

because `dimnames` must be a list.

Is it true that this is an array?

array(1:6, dim=c(2,2,2), dimnames=list("rows","columns","groups")

no

because `dimnames` does not have a value for each component of each dimension.

Is it true that this is an array?

array(1:6, dim=c(2,2,2), dimnames=list(c("row1","row2"),c("col1","col2"),c("group1","group2")))

yes

because `dimnames` has a value for each component of each dimension.