# Parabolic SAR

`sar`

Trailing stop-and-reverse level that speeds up as the trend runs.

## Inputs

| Name | Type | Default | Range |
| --- | --- | --- | --- |
| af_step | float | 0.02 | 0.001 to 1 |
| af_max | float | 0.2 | 0.01 to 1 |

## Outputs

| Name | Kind |
| --- | --- |
| sar | value |

Warm-up: 1 bars (1 at the defaults).

Repaints: No.

## Formula

SAR[i+1] = SAR[i] + AF * (EP - SAR[i]), EP = the extreme price of the trend

AF starts at the step, grows by the step with each new extreme and stops at the maximum.

A reversal restarts EP and AF. The first leg is seeded short and is left empty until the first reversal the price itself causes.