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# GAMMADIST: Gamma Distribution CDF
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| Property | Value |
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| ---------------- | -------------------------------- |
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| **Category** | Numeric |
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| **Inputs** | Source (close) |
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| **Parameters** | `alpha` (default 2.0), `beta` (default 1.0), `period` (default 14) |
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| **Outputs** | Single series (Gammadist) |
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| **Output range** | Varies (see docs) |
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| **Warmup** | `period` bars |
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### TL;DR
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- The Gamma Distribution CDF transforms a min-max normalized price into the cumulative distribution function of the gamma distribution, producing an ...
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- Parameterized by `alpha` (default 2.0), `beta` (default 1.0), `period` (default 14).
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- Output range: Varies (see docs).
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- Requires `period` bars of warmup before first valid output (IsHot = true).
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- Validated against TA-Lib, Skender, and Tulip reference implementations where available.
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The Gamma Distribution CDF transforms a min-max normalized price into the cumulative distribution function of the gamma distribution, producing an output in $[0, 1]$. The gamma distribution generalizes the exponential distribution by adding a shape parameter $\alpha$ that controls whether the PDF is monotonically decreasing ($\alpha < 1$), exponential ($\alpha = 1$), or bell-shaped with a right skew ($\alpha > 1$). Combined with a rate parameter $\beta$ that scales the normalized input, GAMMADIST provides a flexible nonlinear mapping with controllable asymmetry. The CDF is computed via the regularized lower incomplete gamma function using series expansion or Lentz continued fraction, selecting the faster-converging method based on the argument relative to the shape parameter.
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## Historical Context
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