# `TAlib.Indicators.Keltner`
[🔗](https://github.com/benyblack/talib/blob/main/lib/indicators/keltner.ex#L1)

Keltner Channels [Wikipedia](https://en.wikipedia.org/wiki/Keltner_channel).

* middle = EMA(close, period)
* upper = middle + mult * ATR(period)
* lower = middle - mult * ATR(period)

The EMA and ATR are both seeded at index `period - 1`, so the channels
are defined for the same points. Bars are maps with at least `:high`,
`:low` and `:close`. See `TAlib` for the remaining conventions:
chronological order, oldest first, `nil` when there is not enough data.

# `keltner`

```elixir
@spec keltner([map()], pos_integer(), number()) ::
  %{upper: float(), middle: float(), lower: float()} | nil
```

Calculate the latest Keltner Channels as a map.

## Parameters

  - bars: list of bars, oldest first.
  - period: EMA/ATR lookback window, a positive integer (default 20).
  - mult: ATR multiplier, a number (default 2).

## Examples

    iex> bars = [
    ...>   %{high: 12, low: 8, close: 10},
    ...>   %{high: 11, low: 9, close: 10},
    ...>   %{high: 13, low: 9, close: 12}
    ...> ]
    iex> %{upper: u, middle: m, lower: l} = TAlib.Indicators.Keltner.keltner(bars, 2, 2)
    iex> {Float.round(u, 4), Float.round(m, 4), Float.round(l, 4)}
    {17.3333, 11.3333, 5.3333}

# `keltner_list`

```elixir
@spec keltner_list([map()], pos_integer(), number()) :: [map() | nil]
```

Calculate the full Keltner Channels series.

Returns a list aligned with `bars`: the first `period - 1` entries are
`nil`, and every later entry is a map with `:upper`, `:middle` and
`:lower`.

## Parameters

  - bars: list of bars, oldest first.
  - period: EMA/ATR lookback window, a positive integer (default 20).
  - mult: ATR multiplier, a number (default 2).

## Examples

    iex> bars = [
    ...>   %{high: 12, low: 8, close: 10},
    ...>   %{high: 11, low: 9, close: 10},
    ...>   %{high: 13, low: 9, close: 12}
    ...> ]
    iex> TAlib.Indicators.Keltner.keltner_list(bars, 2) |> Enum.count(&is_nil/1)
    2

---

*Consult [api-reference.md](api-reference.md) for complete listing*