Conditionals in R

Introduction

Conditionals are an important feature in R. This section corresponds to Datacamp’s Conditionals and Control Flow in the Intermediate R course.

Equality Tests

• Equality is == and inequality is !=
• Comparisons are < and >
• Comparisons with equal are <= and >=

Testing different types

• String
  • Alphabetical, with "a" < "b"
  • Capitalization matters, with "a" < "A" (lowercase are less)
• Boolean
  • TRUE is 1, and FALSE is 0
  • So TRUE > FALSE
• Vector
  • Pairwise, so c(1, 2) < c(2, 3) returns c(TRUE, TRUE)
• Matrix
  • Pairwise, so they return a TRUE/FALSE matrix.
• Types
  • R will automatically convert between types, so "1" == 1
  • Be careful with Booleans! The type conversions don’t always work. For example, 1 == TRUE but "1" != TRUE
• sum() can count the number of TRUE in a vector/matrix

Logical operators

• AND
  • Use & (preferred)
  • Use && to test the first element of a vector/matrix.
• OR
  • Use | (vertical pipe)
  • Use || to test the first element of a vector/matrix.
• NOT
  • Use !

If Statement

You can use the if statement to selectively execute code. You can use a combination of if, else if, and else.

var_a <- 100

if (var_a < 100) {
  print("less than 100")
} else if (var_a > 200) {
  print("greater than 200")
} else {
  print("otherwise")
}