# LAB: Matrices and DataFrames

This is the lab associated with the lecture and lesson on Matrices and Dataframes in R.

Please upload your final completed lab on the Assignments page in Canvas, as per the instructions below.

You are welcome and expected to ask for help from the instructors if you get stuck: Please also come to the R Bootcamp on Friday—there is coffee and snacks!

## Questions

A. First, let’s go over matrices.

1. Generate a vector from 2 to 40, in steps of 2s.

2. Use this vector to create a matrix with 4 columns.

3. What are the dimensions of the matrix?

4. Sum all values of the second row with the `sum()` function.

5. Find the mean of all values of the 4th column.

6. Give the matrix column names of a, b, c, and d in that order.

B. Now refer to the original Harry Potter Movies Table

Table 1. Box office history for all Harry Potter movies.

Release Date Movie Production Budget Domestic Opening Weekend Domestic Box Office Worldwide Box Office
Nov 16, 2001 Harry Potter and the Sorcerer’s Stone \$125,000,000 \$90,294,621 \$317,575,550 \$974,755,371
Nov 15, 2002 Harry Potter and the Chamber of Secrets \$100,000,000 \$88,357,488 \$261,987,880 \$878,979,634
Jun 4, 2004 Harry Potter and the Prisoner of Azkaban \$130,000,000 \$93,687,367 \$249,538,952 \$796,688,549
Nov 18, 2005 Harry Potter and the Goblet of Fire \$150,000,000 \$102,685,961 \$290,013,036 \$896,911,078
Jul 11, 2007 Harry Potter and the Order of the Phoenix \$150,000,000 \$77,108,414 \$292,004,738 \$942,943,935
Jul 15, 2009 Harry Potter and the Half-Blood Prince \$250,000,000 \$77,835,727 \$301,959,197 \$935,083,686
Nov 19, 2010 Harry Potter and the Deathly Hallows: Part I \$125,000,000 \$125,017,372 \$295,983,305 \$960,283,305
Jul 15, 2011 Harry Potter and the Deathly Hallows: Part II \$125,000,000 \$169,189,427 \$381,011,219 \$1,341,511,219
Nov 18, 2016 Fantastic Beasts and Where to Find Them \$180,000,000 \$74,403,387 \$234,037,575 \$803,798,342

Source: http://www.the-numbers.com/movies/franchise/Harry-Potter#tab=summary

1. Create a data frame from vectors of the movie titles, production budget, and worldwide box office

2. Add a fourth column to your data frame, representing the global return on investment of each film. Do this without creating an entirely new data frame.

3. Look at the structure of your data frame. What is the data class of each column?

4. What is the average return on investment across all movies? How much did Warner Bros profit from the entire franchise?

5. Which movies had a worldwide box office less than 900,000,000? Greater than 1,000,000,000?