DataTypes.pdf

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Introduction to the R Language
Data Types and Basic Operations
Roger Peng, Associate Professor
Johns Hopkins Bloomberg School of Public Health
Objects
R has five basic or “atomic” classes of objects:
·
character
·
numeric (real numbers)
·
integer
·
complex
·
logical (True/False)
The most basic object is a vector
·
A vector can only contain objects of the same class
·
BUT: The one exception is a
list,
which is represented as a vector but can contain objects of
different classes (indeed, that’s usually why we use them)
Empty vectors can be created with the
vector()
function.
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Numbers
·
Numbers in R a generally treated as numeric objects (i.e. double precision real numbers)
·
If you explicitly want an integer, you need to specify the
L
suffix
·
Ex: Entering
1
gives you a numeric object; entering
1L
explicitly gives you an integer.
·
There is also a special number
Inf
which represents infinity; e.g.
1 / 0
;
Inf
can be used in
ordinary calculations; e.g.
1 / Inf
is 0
·
The value
NaN
represents an undefined value (“not a number”); e.g. 0 / 0;
NaN
can also be
thought of as a missing value (more on that later)
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Attributes
R objects can have attributes
·
names, dimnames
·
dimensions (e.g. matrices, arrays)
·
class
·
length
·
other user-defined attributes/metadata
Attributes of an object can be accessed using the
attributes()
function.
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Entering Input
At the R prompt we type expressions. The
<-
symbol is the assignment operator.
> x <-
1
> print(x)
[1]
1
> x
[1]
1
> msg <-
"hello"
The grammar of the language determines whether an expression is complete or not.
> x <-
## Incomplete expression
The # character indicates a comment. Anything to the right of the # (including the # itself) is ignored.
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