Suppose we have defined a list object, "X", which has 3 components. Each component is a vector with at least 5 elements. Which command will extract the fourth (4th) element from the third (3rd) component of our list?

What is the output of the following calculation? t(c(1, 1)) %*% c(1, 1)

Let X be a n-dimension vector. Which call tests this particular statement: "no value of X is NA"

Arrays are similar to matrices in R, but are different in what respect?

What values are displayed for the x-axis limits of the following plot? plot(c(0, 2), c(0, 1), xaxt="n", yaxt="n"); axis(side=2, labels=c("0", "10"), at=c(0,1))

What is the output of: rrr <- 5.45667; sprintf("%1.f", round(rrr, 3))

Given x <- c(1:3,NA), the command: (x+1)[(!is.na(x)) & x>0] -> z generates:

Which is an invalid way to return the mean of each variable in a numeric data frame?

Which is NOT the parameter of command seq()?

What is the output of the command: paste("O", "M", "G")

The function "rescale()" exists in both the plotrix and psych packages. How can I ensure that the plotrix version is used to scale my vector "X" to between 1 and 2?