02-functions-instructor-notes.md

02-functions Instructor notes

How to write functions in R?

When demonstrating how to write the function to convert the temperature, go slowly and demonstrate how to do it in steps in RStudio. For instance, start by taking one of the numeric examples, replace the number by the variable temp, explain that temp doesn't exist in the global environment, and that we will be creating it by enclosing it into a function:

1. (temp - 32) * 5/9

2.  function(temp) {
    	(temp - 32) * 5/9
    	}
   

After flashing the first function for temperature conversion:

• Demonstrate default values: show how convert_fahr() doesn't work.
• Change function to have default value for the temperature (e.g., temp = 0 and to = "celcius", and show how now convert_fahr() works.
• Use this to expand on using match.arg coming up.

After refactoring of the functions, before weight conversion challenge

• Demonstrate scoping:
  • Show that there is no variable to, temp or res in the global environment.
  • Then assign a value to the variable to or res and show that it doesn't affect the behavior of the function.