From c834704d89f322a38da6f2f80a450a31205ae29c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Deronne?= <sebastien.deronne@gmail.com>
Date: Sun, 7 Jan 2024 10:21:49 +0100
Subject: [PATCH] core: Add functions to calculate mean for Weibull
 distribution

---
 src/core/model/random-variable-stream.cc | 14 ++++++++++++++
 src/core/model/random-variable-stream.h  | 13 +++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/src/core/model/random-variable-stream.cc b/src/core/model/random-variable-stream.cc
index 4364419ea..699f98242 100644
--- a/src/core/model/random-variable-stream.cc
+++ b/src/core/model/random-variable-stream.cc
@@ -612,6 +612,20 @@ WeibullRandomVariable::GetBound() const
     return m_bound;
 }
 
+double
+WeibullRandomVariable::GetMean(double scale, double shape)
+{
+    NS_LOG_FUNCTION(scale << shape);
+    return scale * std::tgamma(1 + (1 / shape));
+}
+
+double
+WeibullRandomVariable::GetMean() const
+{
+    NS_LOG_FUNCTION(this);
+    return GetMean(m_scale, m_shape);
+}
+
 double
 WeibullRandomVariable::GetValue(double scale, double shape, double bound)
 {
diff --git a/src/core/model/random-variable-stream.h b/src/core/model/random-variable-stream.h
index 7ddb6f9e7..01bffd629 100644
--- a/src/core/model/random-variable-stream.h
+++ b/src/core/model/random-variable-stream.h
@@ -862,6 +862,19 @@ class WeibullRandomVariable : public RandomVariableStream
      */
     double GetBound() const;
 
+    /**
+     * \brief Returns the mean value for the Weibull distribution returned by this RNG stream.
+     * \return The mean value for the Weibull distribution returned by this RNG stream.
+     */
+    double GetMean() const;
+
+    /**
+     * \copydoc GetMean()
+     * \param [in] scale Scale parameter for the Weibull distribution.
+     * \param [in] shape Shape parameter for the Weibull distribution.
+     */
+    static double GetMean(double scale, double shape);
+
     /**
      * \copydoc GetValue()
      * \param [in] scale Scale parameter for the Weibull distribution.