What R function can be used to tabulate values of categorical variable Y (columns) by categorical variable X (rows), including missing values?

Which R code subsets a matrix Y to only those records (rows) where a variable x (in Y) is less than 100?

Which one is the correct expression regarding outer product of two arrays?

Which of the following is NOT one of R's basic vector types?

Which of the following statements regarding mixed vector and array arithmetic is true?

To test the residuals of a regression model X for heteroscedastisity, you can use this command:

I want to use the sort() function, and I see in the help file that I my sort "an R object with a class, or a numeric, complex, character, or logical vector." Given this guidance, which is a valid call to sort()?

Which object class can contain multiple unrelated object classes of potentially different sizes?

Which R command is used to merge two data sets X and Y by the variable "ID" that includes all records from both data sets?

Suppose numeric vectors X, Y, and Z are all of the same length. Which R command will create a matrix with rows X, Y, Z?

Which R function will generate a mean for each row in a numeric matrix X with intermittent missing values?