The Aroon Oscillator condenses the struggle between the "Aroon Up" and "Aroon Down" lines into a single, normalized value. It quantifies not just the existence of a trend, but its freshness. It answers the question: "Are new highs appearing faster than new lows?"
Introduced by Tushar Chande in *The New Technical Trader* (1995), the Aroon system was a departure from price-based momentum. It focused on *time*. While RSI asks "how much did price move?", Aroon asks "how long has it been since the last extreme?". The Oscillator is simply the arithmetic difference between the two, providing a zero-centered metric for trend bias.
## Architecture & Physics
The physics of Aroon are temporal, not spatial. It measures the decay of "recency."
2.**Normalization**: These counts are converted to a 0-100 scale (100 = happened right now, 0 = happened `Period` bars ago).
3.**Differential**: The Oscillator is `Up - Down`.
### The Drift Resistance
Unlike recursive indicators (EMA, RSI) which accumulate floating-point errors over time, Aroon is stateless in the long term. Its value depends *only* on the data within the lookback window. This makes it mathematically robust and immune to "poisoning" from bad data in the distant past.
The implementation uses a circular buffer (`RingBuffer`) to store historical highs and lows, ensuring O(1) access and zero heap allocations during the update cycle. The min/max search is performed in-place on the buffer.
- **Lag**: Because it looks back `Period` bars, it will not signal a reversal until the previous extreme "ages out" or is superseded. It is a lagging indicator of trend changes.
- **Flatlining**: In strong trends, the oscillator can peg at +100 or -100 for extended periods. This is a feature, not a bug—it indicates a "fresh" extreme on every bar.
