# Representing missing data

```@meta
CurrentModule = DataArrays
```

```@docs
NA
NAtype
```

## Arrays with possibly missing data

```@docs
AbstractDataArray
AbstractDataVector
AbstractDataMatrix
DataArray
DataVector
DataMatrix
@data
isna
dropna
padna
levels
```

## Pooled arrays

```@docs
PooledDataArray
@pdata
compact
setlevels
setlevels!
replace!
PooledDataVecs
getpoolidx
reorder
```
