• Did you notice anything weird while finishing the Choice Operations exercise?
• Take a closer look at item 4.

Floating point

> x <- 1.3
> y <- 2.8
>  x * 2 + 0.2 == y
[1] FALSE
> 1.3 * 2 + 0.2
[1] 2.8

• What’s going on?
• Unexpected result from computer arithmetic
• Numbers combine to include very small trailing digit
• See this more easily in Python

>>> 1.3 * 2 + 0.2 == 2.8
False
>>> 1.3 * 2 + 0.2
2.8000000000000003

Testing equality with decimals

• round(x * 2 + 0.2, 1) == y
• all.equal(x * 2 + 0.2, y)