From ff0105182d8f0b23398efd00f9437dd3dcb07d91 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?L=C3=A9a=20Saviot?= <lea.saviot@numworks.com>
Date: Mon, 26 Aug 2019 10:14:38 +0200
Subject: [PATCH] [apps/proba] P(X<?) = 0 gives 0 for ChiSquaredDistribution

---
 apps/probability/distribution/chi_squared_distribution.cpp | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/apps/probability/distribution/chi_squared_distribution.cpp b/apps/probability/distribution/chi_squared_distribution.cpp
index ce7769f53..d1770caac 100644
--- a/apps/probability/distribution/chi_squared_distribution.cpp
+++ b/apps/probability/distribution/chi_squared_distribution.cpp
@@ -69,6 +69,9 @@ double ChiSquaredDistribution::cumulativeDistributiveInverseForProbability(doubl
    *         => b^(k/2) > k/2 * 2^(k/2) * proba * gamma(k/2)
    *         => exp(k/2 * ln(b)) > k/2 * 2^(k/2) * proba * gamma(k/2)
    *         => b > exp(2/k * ln(k/2 * 2^(k/2) * proba * gamma(k/2))) */
+  if (*probability < DBL_EPSILON) {
+    return 0.0;
+  }
   const double k = m_parameter1;
   const double ceilKOver2 = std::ceil(k/2.0f);
   const double kOver2Minus1 = k/2.0f - 1.0f;