Chapter 9 Caution with parsing statements

What do you think will happen if we try the code below?

if(2+2) == 4 
print("Arithmetic works.")
else 
print("Houston, we have a problem.")

## Error: <text>:1:9: unexpected '=='
## 1: if(2+2) ==
##             ^

This does not work because R evaluates the first line and does not know that you are going to use an else statement

Use curly brackets { } so that R knows to expect more input. Try:

if (2 + 2 == 4) {
    print("Arithmetic works.")
} else {
    print("Houston, we have a problem.")
}

## [1] "Arithmetic works."