Week 2 Quiz >> R Programming
1. Suppose I define the following function in R
cube <- function(x, n) {
x^3
}
What is the result of running
cube(3)
in R after defining this function?
- An error is returned because ‘n’ is not specified in the call to ‘cube’
- The number 27 is returned
- The users is prompted to specify the value of ‘n’.
- A warning is given with no value returned.
2. The following code will produce a warning in R.
x 5) {
x <- 0
}
Why?
- ‘x’ is a vector of length 10 and ‘if’ can only test a single logical statement.
- The syntax of this R expression is incorrect.
- The expression uses curly braces.
- There are no elements in ‘x’ that are greater than 5
- You cannot set ‘x’ to be 0 because ‘x’ is a vector and 0 is a scalar.
3. Consider the following function
f <- function(x) {
g <- function(y) {
y + z
}
z <- 4
x + g(x)
}
If I then run in R
z <- 10
f(3)
What value is returned?
- 4
- 7
- 16
- 10
4. Consider the following expression:
What is the value of ‘y’ after evaluating this expression?
x <- 5
y <- if(x < 3) {
NA
} else {
10
}
- 5
- 10
- NA
- 3
5. Consider the following R function
Which symbol in the above function is a free variable?
h <- function(x, y = NULL, d = 3L) {
z <- cbind(x, d)
if(!is.null(y))
z <- z + y
else
z <- z + f
g <- x + y / z
if(d == 3L)
return(g)
g <- g + 10
g
}
- f
- z
- d
- L
- g
6. What is an environment in R?
- a collection of symbol/value pairs
- a special type of function
- a list whose elements are all functions
- an R package that only contains data
7. The R language uses what type of scoping rule for resolving free variables?
- dynamic scoping
- global scoping
- lexical scoping
- compilation scoping
8. How are free variables in R functions resolved?
- The values of free variables are searched for in the environment in which the function was defined
- The values of free variables are searched for in the global environment
- The values of free variables are searched for in the working directory
- The values of free variables are searched for in the environment in which the function was called
9. What is one of the consequences of the scoping rules used in R?
- Functions cannot be nested
- All objects must be stored in memory
- R objects cannot be larger than 100 MB
- All objects can be stored on the disk
10. In R, what is the parent frame?
- It is the environment in which a function was called
- It is the environment in which a function was defined
- It is always the global environment
- It is the package search list
