Control Flow

After reading these notes you should be able to:

if

Spring 2022 Readers: Dave tried to write too many notes this week. Please read the following in place of this under construction section:

if (condition) code_to_evaluate
if (TRUE) print("Hello, World!")
[1] "Hello, World!"
if (FALSE) print("Hello, World!")
if (42) print("Hello, World!")
[1] "Hello, World!"
if ("foo") print("Hello, World!")

else

Spring 2022 Readers: Dave tried to write too many notes this week. Please read the following in place of this under construction section:

x = 42
if (x > 50) {
  y = 1
} else {
  y = 0
}
y
[1] 0
  • TODO: do something “else” if condition not met
  • TODO: can be chained with additional ifs

switch

  • TODO: we won’t do this in a quiz or exam, so not currently needed

ifelse

Spring 2022 Readers: Dave tried to write too many notes this week. Please read the following in place of this under construction section:

  • TODO: “vectorized” if-else
ifelse(test = 42 > 2, yes = "!", no = "?")
[1] "!"
ifelse(test = 2 > 42, yes = "!", no = "?")
[1] "?"
  • TODO: full vector example
  • TODO: vector example with recycling
ifelse(1:10 %% 2 == 0, "even", "odd")
 [1] "odd"  "even" "odd"  "even" "odd"  "even" "odd"  "even" "odd"  "even"

Loops

Loops (for, while, and repeat) are another form of control flow. We will put off discussing these until next chapter so that we can first introduce the apply functions as a more common R approach to performing the types of operations usually done in other languages with loops.

Summary

  • TODO: You’ve learned to…

What’s Next?

  • TODO: iteration

TODO

  • TODO: ?