Data Analysis with R, Second Edition - Second Edition

Logicals and characters

So far, we've only been dealing with numerics, but there are other atomic data types in R:

   > foo <- TRUE        # foo is of the logical data type 
   > class(foo)         # class() tells us the type 
   [1] "logical" 
   > bar <- "hi!"       # bar is of the character data type 
   > class(bar) 
   [1] "character" 

The logical data type (also called Booleans) can hold the values TRUE or FALSE or, equivalently, T or F. The familiar operators from Boolean algebra are defined for these types:

   > foo 
   [1] TRUE 
   > foo && TRUE                 # boolean and 
   [1] TRUE 
   > foo && FALSE 
   [1] FALSE 
   > foo || FALSE                # boolean or 
   [1] TRUE 
   > !foo                        # negation operator 
   [1] FALSE 

In a Boolean expression with a logical value and a number, any number that is not 0 is interpreted as TRUE: