Overview

Teaching: 5 min
Exercises: 10 min

Questions

• How do I set up an if/else statement?

Objectives

• Learn both the if/else and ifelse styles of setting up a decision statement

#If/else two ways

The if/else statement is frequently used in programming and there are a couple of ways to do it in R. The classical style is in the following example.

x = -5
if(x > 0){
   print("Non-negative number")
} else {
   print("Negative number")
}

A shortcut for simple if/else statement is the ifelse function

ifelse(x>0, "Non-negative number", "Negative number")

The if/else statement can have nesting as well

if (x < 0) {
   print("Negative number")
} else if (x > 0) {
   print("Positive number")
} else {
   print("Zero")
}

On your own

The Fibonacci numbers are the sequence of numbers defined by the linear recurrence equation Fn = Fn−1 + Fn−2 where F1 = F2 = 1. So the first 5 terms are 1, 1, 2, 3, 5. Using a for loop and if statement, generate the first 8 terms of the Fibonacci sequence. No cheating by starting off with a c(1,1) vector and adding to it :)

Summary of functions

Key Points

• ifelse() is a great shortcut if you have a simple statement