Getting help

Each R function comes with its own documentation that explains what it does and how to use it. Documentation in R takes some getting used to, but once you learn the patterns it becomes a valuable resource to coders new and experienced. After you complete this exercise, you will know how to:

Where to find help

There are two ways to find documentation: the help pane and the ? operator. Run this command at the console:

?ifelse

This will bring up the documentation for the ifelse() function in the help pane. You can also use this pane directly.

Anatomy of documentation

Documentation has many parts, but focus on these key ones:

  • Big picture: Description comes first and provides a high-level description of the function.
  • Input: Arguments lists the function’s parameters, telling you what inputs it expects to receive.
  • Output: Value describes what the function returns.
  • In practice: Examples shows how to use the function with sample code.

Examples is particularly helpful. Seeing a function in action is often the best way to pick up how to use it. Think of them as code sleuth activities in the real world.

Read the documentation for ifelse() to answer these questions.

  • How many parameters does the function take?
  • Do any of the parameters have default values?

Practice reading documentation

This exercise asks you to stand up, walk around, and talk to your peers.

You’ve been assigned to one of four groups based on your last name. Find one or two other students in the same group as you. As a team, follow the instructions below based on your group.

Last name begins A-F

Read the documentation for log().

Use the documentation to answer the following questions:

  • What’s the default base for the log() function?
  • What’s the difference between log(), log2(), and log10()?
  • How would you use log() to do the same thing as log10()?

Last name begins G-L

Read the documentation for which.max().

Use the documentation to answer the following questions:

  • What’s the difference between which.max() and max()?
  • You’re given a vector of 100 2d6 dice rolls. How would you use which.max() to find the first roll that’s 10 or greater?

Last name begins M-R

Read the documentation for startsWith().

Use the documentation to answer the following questions:

  • What type of vectors does startsWith() expect as input?
  • What type of vector does startsWith() return?
  • How would you use startsWith() to check if a bird name begins with “California”? Write a line of code to demonstrate its use.

Last name begins S-Z

Read the documentation for cumsum().

Use the documentation to answer the following questions:

  • What’s the difference between cumsum() and sum()?
  • sum(1:5) returns one value. How many values are in the vector returned by cumsum(1:5)?

Practice reading documentation

Stick with the student(s) you practiced reading documentation with. Find students from the other three groups. Trade off explaining your assigned functions.