# Parabolic SAR (PSAR)

> QuantNexus indicator page for the PSAR reversal and trailing stop line.

**Route**: `/quantnexus/indicators/psar/`

## What It Does

PSAR provides a trailing stop style line that can also act as a reversal trigger. It is common in trend-following and exit management systems.

## Formula

PSAR iteratively projects a stop-and-reversal level using the current trend direction, acceleration factor, and extreme price.

## Parameters

- `period` - default `2`
- `af` - default `0.02`
- `afmax` - default `0.2`

## C++23 API

```cpp
#include <nonabt/indicators/psar.hpp>
auto psar = std::make_unique<nonabt::PSAR>(data(), 2, 0.02, 0.2);
```

## Common Usage

- Use PSAR as a trailing stop.
- Use a price cross through PSAR as a trend reversal trigger.
- Works best when the market is already trending.

## Practical Pattern

Buy while price stays above PSAR and exit or reverse when price falls below it.