# Envelopes

`envelopes`

A moving average with a band a set distance above and below it.

## Inputs

| Name | Type | Default | Range |
| --- | --- | --- | --- |
| source | source | close |  |
| period | int | 14 | 1 to 5000 |
| deviation | float | 0.1 | 0 to 100 |
| method | ma_method | sma |  |
| mode | choice | percent |  |

## Outputs

| Name | Kind |
| --- | --- |
| upper | value |
| middle | value |
| lower | value |

Warm-up: pick(method, {'sma': period - 1, 'ema': period - 1, 'smma': period - 1, 'lwma': period - 1, 'wma': period - 1, 'hma': period + round_half_up(sqrt(period)) - 2, 'dema': 2 * period - 2, 'tema': 3 * period - 3}) bars (13 at the defaults).

Repaints: No.

## Formula

middle = the moving average named by method

percent: upper = middle * (1 + deviation / 100), lower = middle * (1 - deviation / 100)

fixed: upper = middle + deviation, lower = middle - deviation