1.2 Following along

Hands–on practice is the only way to gain competence in using R for data analysis. With that in mind, we present R code and output throughout the guide. These serve as (hopefully) useful examples for reference and, most importantly, as an opportunity to practice on your own. When you see a code chunk and output, we want you to follow along by entering the code on your computer and comparing your output to what's given in the guide. Consider a chunk like the one below:

# Summarize miles per gallon (mpg)
  summary(mtcars$mpg)

##    Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
##    10.4    15.4    19.2    20.1    22.8    33.9

Throughout the text, you’ll find that annotation and comments follow a single # and appear in light blue:

# Summarize miles per gallon (mpg)

The actual R commands, below, come in a mix of black, dark blue, and other accent colors. Where possible, they are shown within a pink box. Type and execute these commands in R as you follow along with the guide.

  summary(mtcars$mpg)

The output from the commands—what you will see in the console window after executing—follows ##.

##    Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
##    10.4    15.4    19.2    20.1    22.8    33.9

Be sure to check your output against what you find here. If your output is different, or if you get an error message, review your code for typos and errors.