# Down Day (DOWNDAY)

> QuantNexus indicator page for DOWNDAY.

**Route**: `/quantnexus/indicators/downday/`

## What It Does

DOWNDAY measures whether the current bar closed lower than the prior bar. It is a simple directional utility indicator.

## Formula

`Down Day = 1 when Close < Previous Close, otherwise 0`

## Parameters

- `period` - default `14`

## C++23 API

```cpp
#include <nonabt/indicators/downday.hpp>
auto downday = std::make_unique<nonabt::DOWNDAY>(data(), 14);
```

## Common Usage

- Use DOWNDAY for direction counting.
- Combine it with rolling windows.
- Useful as a Boolean input to custom logic.

## Practical Pattern

A high count of down days can indicate persistent selling pressure.