4.6 Logical Tests and Comparators

As mentioned above, R recognizes logical values as a distinct type. R provides all the conventional infix logical operators:

1 == 1 # equality
[1] TRUE
1 != 1 # inequality
[1] FALSE
1 < 2 # less than
[1] TRUE
1 > 2 # greater than
[1] FALSE
1 <= 2 # less than or equal to
[1] TRUE
1 >= 2 # greater than or equal to

These operators also work on vectors, albeit with the same caveats about vector length as noted earlier:

x <- c(1,2,3)
x == 2
[1] FALSE TRUE FALSE
x < 1
[1] FALSE FALSE FALSE
x < 3
[1] TRUE TRUE FALSE
c(1,2) == c(1,3)
[1] TRUE FALSE
c(1,2) != c(1,3)
[1] FALSE TRUE
c(1,2) == c(1,2,3)
[1] TRUE TRUE FALSE
Warning message:
In c(1, 2, 3) == c(1, 2) :
  longer object length is not a multiple of shorter object length

R also provides many functions of the form is.X where X is some type or condition (recall that . is not a special character in R):

is.numeric(1) # is the argument numeric?
[1] TRUE
is.character(1) # is the argument a string?
[1] FALSE
is.character("ABC")
[1] TRUE
is.numeric(c(1,2,3)) # recall a vector has exactly one type
[1] TRUE
is.numeric(c(1,2,"3"))
[1] FALSE
is.na(c(1,2,NA))
[1] FALSE FALSE TRUE

Quick-R - Operators