R Types

• Here we just introduce some basic "atomic" data types. There are many more, like dates and time series.

• Use function is.x(), such as is.na() and is.complex(), to test the type of an R object.

Integer

Long-storage integers are written with L (otherwise they will be numerics)

class(5L) # "integer"

Numeric

A "numeric" is a double-precision floating-point number.
Scientific notations, infinities, and Not-a-Number are supported.

5e4
1.6e-35
Inf
class(-Inf)
class(NaN)

Complex

The imaginary part of a complex is appended with an i in R.

x <- 1 + 1i
y <- -1i + 1
x * y
class(x - 1i) # complex

Characters

There is no difference between strings and characters in R, unlike MATLAB.
And a string and a character are both char vectors of length 1.
Characters are surrounded by double quotes " (or single quotes ').

length("Hello")
length(c("Hello","World"))

Logical

Capital TRUE, FALSE, and NA are three logicals in R

TRUE # not true or True
class(NA)
FALSE == FALSE # TRUE

• T and F are shorthands for TRUE and FALSE.

Factors

Factors are used to represent EDAV - Categorical Data and can be unordered or ordered. One can think of a factor as an integer vector where each integer has a label.

x <- factor(c("yes", "yes", "no", "yes", "no")) 
x
# [1] yes yes no  yes no 
# Levels: no yes
## The "levels" are the values the categorical data can take
levels(x)

table(x) 
# x
# no yes 
#  2   3 
## See the underlying representation of a factor
unclass(x)
# 2 2 1 2 1
# attr(x,"levels")
# [1] "no"  "yes"

• Factor levels have an order
  • Not like #Characters, which obey alphabetical order
• Factor levels serve as labels for data
• forcats is a useful package for manipulating factors

NULL

Capital NULL is a special empty object in R.

by zcysxy