Donchian Reversal Signals with Labels

Overview:
This indicator is designed to identify potential reversal signals based on price action relative to two Donchian Channels. It plots **"BUY"** and **"SELL"** labels on the chart when specific conditions are met, helping traders spot potential trend reversals.

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Key Features:
1. Dual Donchian Channels:
- The indicator uses two Donchian Channels with user-defined lengths (`length1` and `length2`).
- The upper band of each channel is the highest high over the specified period.
- The lower band of each channel is the lowest low over the specified period.

2. Reversal Signals:
- A yellow "BUY" label appears below a green (bullish) candle if:
- The previous candle is red (bearish).
- The previous red candle touches or breaches either of the lower Donchian Channels.
- A green "SELL" label appears above a red (bearish) candle if:
- The previous candle is green (bullish).
- The previous green candle touches or breaches either of the upper Donchian Channels.

3. Visual Clarity:
- The labels are placed above or below the candles for easy visibility.
- The use of colors (yellow for buy, green for sell) makes it intuitive to interpret the signals.

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How It Works:
1. Donchian Channel Calculation:
- The upper and lower bands of the two Donchian Channels are calculated using the highest high and lowest low over the specified periods (`length1` and `length2`).

2. Candle Color Detection:
- The script identifies whether the current and previous candles are bullish (green) or bearish (red) based on their open and close prices.

3. Signal Conditions:
- For a **"BUY" signal**:
- The current candle must be green.
- The previous candle must be red and touch or breach either of the lower Donchian Channels.
- For a **"SELL" signal**:
- The current candle must be red.
- The previous candle must be green and touch or breach either of the upper Donchian Channels.

4. Label Placement:
- The labels are plotted using `shape.labelup` and `shape.labeldown` for clear visibility.

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Input Parameters:
- **Donchian Channel Length 1 (`length1`)**: The period for the first Donchian Channel (default: 20).
- **Donchian Channel Length 2 (`length2`)**: The period for the second Donchian Channel (default: 34).

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How to Use:
1. Add the indicator to your chart.
2. Adjust the lengths of the Donchian Channels if needed.
3. Look for **"BUY"** and **"SELL"** labels on the chart:
- A **yellow "BUY" label** below a green candle suggests a potential bullish reversal.
- A **green "SELL" label** above a red candle suggests a potential bearish reversal.
4. Use these signals in conjunction with other technical analysis tools for confirmation.

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Example Use Case:
- If the price touches the lower Donchian Channel and forms a red candle, followed by a green candle, a **"BUY" label** will appear, indicating a potential upward reversal.
- If the price touches the upper Donchian Channel and forms a green candle, followed by a red candle, a **"SELL" label** will appear, indicating a potential downward reversal.

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Customization:
- You can modify the lengths of the Donchian Channels to suit your trading style.
- The colors and text of the labels can also be adjusted in the script if desired.

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Disclaimer:
This indicator is designed to assist traders in identifying potential reversal signals. However, it should not be used in isolation. Always confirm signals with additional analysis and risk management strategies.