Exercise 0

Exercise 0.1

We will work with the iris dataset, which contains size measurements of different species of flowers. This dataset is built into R and can be loaded with the simple command below.

data('iris')

Let’s take a look at the data.

Read about these functions, try them on iris, and try to understand their output:

• dim
• length
• names
• summary

Exercise 0.2

Say we want to draw random samples from iris. How do we do this? Go to Google and search for “draw random samples from data frame R”. One of the search results will be the following question on StackOverflow:

https://stackoverflow.com/questions/8273313/sample-random-rows-in-dataframe

Note how different the solutions are. Try loading the dplyr library and using the sample_n() function to draw random samples from iris.

Exercise 0.3

In this exercise we will try to write a script.

• Make a directory structure to store scripts for the exercises: r_for_statistics > exercises
• Make a script in the exercises directory: exercise_0_2.R
• Load the “ggplot2” and “magrittr” libraries
  • If you didn’t already install these, do it now
• Write the following code:
  • ggplot(iris, aes(Sepal.Width)) + geom_histogram(bins=10)
• Try evaluating:
  • A single line of code (ctrl + enter)
  • A block of code (highlight + ctrl + enter)
  • The entire file (ctrl + alt + enter)
• Write comments for the code