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

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

Which is INCORRECT regarding the command: T <- 40; rnorm( T, 1, 4) ?

What is the result of command: z <- c(1:3,NA); ind <- is.na(z); z ?

How does a matrix differ from a data frame?

What value does this statement return? unclass(as.Date("1971-01-01"))

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

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?

What is the output of dim(matrix(1:10, ncol=2))?

What is the output of the following R function? yyy <- c(1, 3, NA); fff <- function(xxx) {mean(xxx)}; fff(yyy)

What does the following R code output? Y <- c(1,2,3); X <- rep(c(1,length(Y)), times=2); X