Knowledge Quiz: Getting Help

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Which section of an R package help file would you reference to learn the order in which the function arguments are specified in the function definition?

The Usage section shows all the possible arguments for a function and the order in which those arguments are defined.

Which section of an R package help file would you reference to learn the default values for a function’s arguments.

Both the Usage and Arguments sections will show the default values for arguments that have default values defined.

Use the following help file excerpt to answer the question below.

cor R Documentation

Correlation, Variance and Covariance (Matrices)

Usage

var(x, y = NULL, na.rm = FALSE, use)

cov(x, y = NULL, use = "everything",
    method = c("pearson", "kendall", "spearman"))

cor(x, y = NULL, use = "everything",
    method = c("pearson", "kendall", "spearman"))

cov2cor(V)

What is the default value for the use argument of the cor() function?

The default value for the use argument is "everything".

  • Wrong: These are all of the possible methods
  • Wrong: This is an argument name
  • Wrong: This is one of the possible methods
  • Correct
  • Wrong: This is one of the possible methods

The dplyr package is installed on your computer, but you have not loaded it in your current R session. Which of the following will successfully open the help file for dplyr’s arrange() function?

  • Incorrect: without loading dplyr first, R doesn’t know which package’s arrange() you mean, so this errors.
  • Correct: the namespace resolution operator (::) tells R exactly which package to search, even if it isn’t loaded.
  • Incorrect: without the package argument or ::, R can’t find arrange() if dplyr isn’t loaded, so this errors.
  • Incorrect: this attempts to call the function (which would also fail, since dplyr isn’t loaded), not open its help file.
  • Correct: explicitly naming the package argument works the same way as ::.
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