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From er...@apache.org
Subject [07/18] commons-numbers git commit: NUMBERS-35: Typo (sign error).
Date Thu, 11 May 2017 12:03:35 GMT
NUMBERS-35: Typo (sign error).

Unit tests are missing (see JIRA issue).

Thanks to Stian Soiland-Reyes for spotting that the code did not
agree with the referenced formula.


Project: http://git-wip-us.apache.org/repos/asf/commons-numbers/repo
Commit: http://git-wip-us.apache.org/repos/asf/commons-numbers/commit/14f6f851
Tree: http://git-wip-us.apache.org/repos/asf/commons-numbers/tree/14f6f851
Diff: http://git-wip-us.apache.org/repos/asf/commons-numbers/diff/14f6f851

Branch: refs/heads/master
Commit: 14f6f851b179249cb74b6dfa5b3c8d193e607186
Parents: f271063
Author: Gilles Sadowski <gilles@harfang.homelinux.org>
Authored: Mon May 8 12:15:07 2017 +0200
Committer: Gilles Sadowski <gilles@harfang.homelinux.org>
Committed: Mon May 8 12:15:07 2017 +0200

----------------------------------------------------------------------
 .../main/java/org/apache/commons/numbers/gamma/Digamma.java    | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)
----------------------------------------------------------------------


http://git-wip-us.apache.org/repos/asf/commons-numbers/blob/14f6f851/commons-numbers-gamma/src/main/java/org/apache/commons/numbers/gamma/Digamma.java
----------------------------------------------------------------------
diff --git a/commons-numbers-gamma/src/main/java/org/apache/commons/numbers/gamma/Digamma.java
b/commons-numbers-gamma/src/main/java/org/apache/commons/numbers/gamma/Digamma.java
index ddcee55..a10f1df 100644
--- a/commons-numbers-gamma/src/main/java/org/apache/commons/numbers/gamma/Digamma.java
+++ b/commons-numbers-gamma/src/main/java/org/apache/commons/numbers/gamma/Digamma.java
@@ -30,11 +30,11 @@ public class Digamma {
     /** S limit. */
     private static final double S_LIMIT = 1e-5;
     /** Fraction. */
-    private static final double F_1_12 = 1d / 12;
+    private static final double F_M1_12 = -1d / 12;
     /** Fraction. */
     private static final double F_1_120 = 1d / 120;
     /** Fraction. */
-    private static final double F_1_252 = 1d / 252;
+    private static final double F_M1_252 = -1d / 252;
 
     /**
      * Computes the digamma function.
@@ -80,7 +80,7 @@ public class Digamma {
         //            1       1        1         1
         // log(x) -  --- - ------ + ------- - -------
         //           2 x   12 x^2   120 x^4   252 x^6
-        digamma += Math.log(x) - 0.5 / x - inv * (F_1_12 + inv * (F_1_120 - F_1_252 * inv));
+        digamma += Math.log(x) - 0.5 / x + inv * (F_M1_12 + inv * (F_1_120 + F_M1_252 * inv));
 
         return digamma;
     }


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