In a linear regression model with outcome y and linear predictors x1, x2, and x3, which R code correctly includes an interaction term between x1 and x2?

Which of the following is NOT included in CRAN's R distribution?

In order to assess whether x and y are equal, you can use the command:

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

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

To test the residuals of model X for autocorrelation of first order, you can use this command:

Which is the INCORRECT way to get the vector [1 1 1 3 3 3 5 5 5]?

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

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

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