Integers v Numerics

  • In R, the integer is a sub-type of numeric
  • R will ONLY use this data type if you EXPLICITLY tell it to
  • And if you don't understand them, they can behave oddly

Integers

  • SQL: INT
  • SAS: No direct analogue

Integers Get Floored

This is the same behavior as the SAS INT command


## What does this code return?
oops <- as.integer(percent_crew)

oops
    

[1] 26

## There are FEW reasons to declare an Integer.

Floating Point "Errors"

How can both statements be correct?


(3 - 2.9)
            

[1] 0.1
            

(3 - 2.9) == 0.1
            

[1] FALSE

See next slide for GORY details.

Floating Point "Errors"

  • As a matter of convention, children are taught a Base 10 (denary) number system
  • Digital computers (must) use a Base 2 (binary) system
  • In Base 2, numbers such as 0.1 are internally held as a floating-point, introducing rounding error
  • See Burns Statistics if you'd like to read more 

print(3 - 2.9, digits=20)
[1] 0.10000000000000008882