## 2.9 Lab 1: Introduction to R Programming

For this lab, we will do several practice problems related to programming in R.

1. Create two vectors as follows

x <- seq(2,10,by=2)
y <- c(3,5,7,11,13)

Add x and y, subtract y from x, multiply x and y, and divide x by y and report your results.

2. The geometric mean of a set of numbers is an alternative measure of central tendency to the more common “arithmetic mean” (this is the mean that we are used to). For a set of $$J$$ numbers, $$x_1,x_2,\ldots,x_J$$, the geometric mean is defined as

$(x_1 \cdot x_2 \cdot \cdots \cdot x_J)^{1/J}$

Write a function called geometric_mean that takes in a vector of numbers and computes their geometric mean. Compute the geometric mean of c(10,8,13)

3. Use the lubridate package to figure out how many days it has been since Jan. 1, 1981.

4. mtcars is one of the data frames that comes packaged with base R.

1. How many observations does mtcars have?

2. How many columns does mtcars have?

3. What are the names of the columns of mtcars?

4. Print only the rows of mtcars for cars that get at least 20 mpg

5. Print only the rows of mtcars that get at least 20 mpg and have at least 100 horsepower (it is in the column called hp)

6. Print only the rows of mtcars that have 6 or more cylinders (it is in the column labeld cyl) or at least 100 horsepower

7. Recover the 10th row of mtcars

8. Sort the rows of mtcars by mpg (from highest to lowest)