Let X be a 3x4 matrix with non-zero values. The result of: > apply(X, 2, mean), is:

Suppose X is the vector c(1:10). Which R code will swap the values of the 3rd element of X and the 7th element of X?

What is the output for the command: > is.na( NaN ) ?

What does the following R function output? xxx <- c(1, 1, 2, 2, 3, 3, NA, NA); yyy <- c(rep(0, 4), rep(1, 4)); cor(yyy, xxx)

Which R function can be used to produce a simple scatterplot of a numeric vector Y versus a numeric vector X?

What is the value of Y? Y <- 10 + 100 & !is.na(0)

Given this named vector "X": > X <- c( 5, 10, 1, 20 ); > names( X ) <- c( "a", "b", "c", "d" ); Which operation is valid to show the 2nd and 4th components of X?

Given the command: Z <- array(h, dim=c(3,4,2)), Z[1:24] stands for:

Which will test the hypothesis that two independent Normally distributed random variables A and B have different means?

Which R function outputs the day of the month from X <- "2014-May-15"?

R operates on named data structures. The simplest such structure is the numeric vector, which is a single entity consisting of an ordered collection of numbers. To set up a vector named x, consisting of 10.4, 5.6, 3.1, 6.4 and 21.7, which is the INCORRECT command: