Which R package combines multi-dimensional arrays?

R code can be tested using the testthat package.

How do you check whether an R object is NULL?

Command lines entered at the console are limited to about _____ bytes.

Which R function lists all values of a variable with their frequencies?

Which of these R functions does NOT allow you to create a matrix?

Which of the following functions merges two variables into one?

You have a 2x2 matrix called M which looks like this:

23 | 41

55 | 77

How do you access the number 41 in the matrix?

Which of the following statements finds the maximum value for each column in a data frame?

When the mean (μ) is ___ and the standard deviation (σ) is ___, we say that the random variable has a standard normal distribution.