From: Ben Pfaff <blp@gnu.org>
Date: Wed, 14 Apr 2004 02:26:37 +0000 (+0000)
Subject: Adjust calculation of kurtosis to avoid subtracting huge numbers from
X-Git-Tag: v0.4.0~279
X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e78d51c7941a26eef71d69260b49eeb1db954428;p=pspp-builds.git

Adjust calculation of kurtosis to avoid subtracting huge numbers from
huge numbers, on Michael Kiefte's advice.
---

diff --git a/src/ChangeLog b/src/ChangeLog
index 1fdf0d54..6db983d6 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,9 @@
+Tue Apr 13 19:24:15 2004  Ben Pfaff  <blp@gnu.org>
+
+	* moments.c (calc_moments): Adjust calculation of kurtosis to
+	avoid subtracting huge numbers from huge numbers, on Michael
+	Kiefte's advice.
+
 Sun Apr 11 14:22:12 2004  Ben Pfaff  <blp@gnu.org>
 
 	Rework moments routines for improved numerical stability based on
diff --git a/src/moments.c b/src/moments.c
index c993f7ae..c4f3fe18 100644
--- a/src/moments.c
+++ b/src/moments.c
@@ -62,9 +62,9 @@ calc_moments (enum moment max_moment,
             }
           if (max_moment >= MOMENT_KURTOSIS && kurtosis != NULL && w > 3.)
             {
-              double g2 = ((w * (w + 1.) * d4
-                            - 3. * pow2 (d2) * (w - 1.))
-                           / ((w - 1.) * (w - 2.) * (w - 3.) * pow2 (s2)));
+              double den = (w - 2.) * (w - 3.) * pow2 (s2);
+              double g2 = (w * (w + 1) * d4 / (w - 1.) / den
+                           - 3. * pow2 (d2) / den);
               if (finite (g2))
                 *kurtosis = g2; 
             }