R Programming Language Certification R Programming Language: Computer Science 4

Question 1

In R, what is the difference between `=` and `<-` for assignment inside a function call?

Accepted Answer

= assigns locally in the call; <- assigns in the current environment

Answer

Inside a function call, = sets a named argument while <- creates a variable in the calling environment.

Question 2

Which R function tests whether an object inherits from a given class?

Accepted Answer

inherits()

Answer

inherits(x, 'classname') returns TRUE if x has the specified class anywhere in its class hierarchy.

Question 3

What is the result of `nchar(NA)` in R?

Accepted Answer

NA

Answer

nchar() propagates NA by default, returning NA when given an NA input.

Question 4

In R, which environment is searched last in the search path?

Accepted Answer

package:base

Answer

package:base is always the last environment on the search path, ensuring base functions are always found.

Question 5

What does `match.arg()` do inside an R function?

Accepted Answer

Validates and partially matches a character argument against predefined choices

Answer

match.arg() validates a character argument against allowed values and supports partial matching.

R Programming Language Certification Practice Test