Knowledge Quiz: Functions

You can recognize a valid function call by the pattern: FUNCTION_NAME().

This is a length-one numeric vector.
This is a symbol (i.e., the name of an object).
Correct. This function call will list the library paths where R will install packages on your system.
Correct. This function call would generate 100 random standard normal deviates.
Correct. This function call would calculate the trimmed mean of x, ignoring any missing values.
This is R’s infinite value code.

Which of the following function calls will correctly round the value 9.8765 to 2 decimal places?

Correct: both arguments are named, so their order doesn’t matter, even though it differs from the previous answer.
Correct: the arguments are supplied in the order round() expects (x, then digits), so no names are needed.
Incorrect: without argument names, R matches by position — the first value fills x and the second fills digits. This call rounds 2 (interpreted as x) to 9.8765 decimal places, which is a nonsensical number of digits, not the intended calculation.
Incorrect: round() expects an argument named digits, not digit. R will not recognize this argument name.
Correct: both arguments are named, so their order doesn’t matter.

Which of the following lines of R code will produce an error when run?

Correct: R is case-sensitive, and there is no function called Sum() (only sum()), so this errors.
Correct: round() has no argument called digit (it’s digits), so this errors.
Incorrect: this is valid, complete R code, so it runs without error.
Incorrect: this is valid, complete R code (digits is the correct argument name), so it runs without error.
Correct: the closing parenthesis is missing, so this errors.