# Data structures

Might be quite brief.

Atomic vectors and lists + data frames.

Most important data types:

* logical
* integer & double
* character
* date
* date time
* factor

<http://adv-r.had.co.nz/OO-essentials.html>

Every vector has three key properties:

1. Type: e.g. integer, double, list.  Retrieve with `typeof()`.
2. Length. Retrieve with `length()`
3. Attributes. A named of list of additional metadata. With the `class` 
   attribute used to build more complex data structure (like factors and 
   dates) up from simpler components. Get with `attributes()`.

## Atomic vectors

### Doubles

```{r}
sqrt(2) ^ 2 - 2

0/0
1/0
-1/0

mean(numeric())
```

## Non-atomic vectors

`class()`

### Factors

(Since won't get a chapter of their own)

### Dates

### Date times

## Lists

## Data frames

## Subsetting

Not sure where else this should be covered.
