Review of Basic Data Analytic Methods Using R - Data Science and Big Data Analytics - page 103

i <- 1 # create a numeric variable
sport <- "football" # create a character variable

flag <- TRUE # create a logical variable

R provides several functions, such as class() and typeof() , to examine the
characteristics of a given variable. The class() function represents the abstract
class of an object. The typeof() function determines the way an object is stored
in memory. Although i appears to be an integer, i is internally stored using double
precision. To improve the readability of the code segments in this section, the
inline R comments are used to explain the code or to provide the returned values.

class(i) # returns "numeric"
typeof(i)

# returns "double"

class(sport) # returns "character"

typeof(sport) # returns "character"

class(flag) # returns "logical"

typeof(flag) # returns "logical"

Additional R functions exist that can test the variables and coerce a variable into a
specific type. The following R code illustrates how to test if i is an integer using the
is.integer() function and to coerce i into a new integer variable, j , using the
as.integer() function. Similar functions can be applied for double, character,
and logical types.

is.integer(i) # returns FALSE
j <- as.integer(i) # coerces contents of i into an
integer
is.integer(j) # returns TRUE

The application of the length() function reveals that the created variables each
have a length of 1. One might have expected the returned length of sport to have
been 8 for each of the characters in the string "football" . However, these three
variables are actually one element, vectors .

length(i) # returns 1

length(flag) # returns 1

length(sport) # returns 1 (not 8 for "football")