From d2ce00de04b275fb49d5c521abceab709a374b06 Mon Sep 17 00:00:00 2001
From: Tim Yates <tyates@picr.man.ac.uk>
Date: Mon, 25 Nov 2013 12:23:33 +0000
Subject: [PATCH] v0.5.5 Bugfix for 0 length collections

---
 README.md                                     |  2 +-
 build.gradle                                  |  2 +-
 .../CollectionExtensionMethods.groovy         | 29 ++++++++++---------
 src/test/groovy/tests/CollectionTests.groovy  | 14 +++++++--
 4 files changed, 30 insertions(+), 17 deletions(-)

diff --git a/README.md b/README.md
index 53d7faf..76e3c2e 100644
--- a/README.md
+++ b/README.md
@@ -9,7 +9,7 @@ Obviously requires at least Groovy 2.0.5 (so that the extension system exists)
 
 Usage:
 
-    @Grab( 'com.bloidonia:groovy-common-extensions:0.5.4' )
+    @Grab( 'com.bloidonia:groovy-common-extensions:0.5.5' )
 
 and the following methods will be available to you:
 
diff --git a/build.gradle b/build.gradle
index dc8c6bb..195d983 100644
--- a/build.gradle
+++ b/build.gradle
@@ -6,7 +6,7 @@ apply plugin: 'signing'
 sourceCompatibility=1.6
 targetCompatibility=1.6
 
-version = '0.5.4'
+version = '0.5.5'
 
 repositories {
   mavenCentral()
diff --git a/src/main/groovy/com/bloidonia/groovy/extensions/CollectionExtensionMethods.groovy b/src/main/groovy/com/bloidonia/groovy/extensions/CollectionExtensionMethods.groovy
index 98b9fbf..3891926 100644
--- a/src/main/groovy/com/bloidonia/groovy/extensions/CollectionExtensionMethods.groovy
+++ b/src/main/groovy/com/bloidonia/groovy/extensions/CollectionExtensionMethods.groovy
@@ -273,11 +273,11 @@ class CollectionExtensionMethods {
   }
 
   @groovy.transform.Immutable( knownImmutables=[ 'median' ])
-  public static class AverageStats<V extends Number> {
-    Double mean
-    V median
-    Double variance
-    Double stdDev
+  public static class AverageStats {
+    BigDecimal mean
+    BigDecimal median
+    BigDecimal variance
+    BigDecimal stdDev
 
     String toString() {
       "AverageStats( mean:$mean, median:$median, variance:$variance, stdDev:$stdDev )"
@@ -300,15 +300,18 @@ class CollectionExtensionMethods {
    * @param collection The {@code Collection} of {@code Number} elements to generate stats for
    * @return           A populated {@code AverageStats} object
    */
-  static <V extends Number> AverageStats<V> average( Collection<V> collection ) {
+  static <V extends Number> AverageStats average( Collection<V> collection ) {
     int size        = collection.size()
-    V sum           = collection.sum()
-    int zsize       = size - 1
-    V median        = size % 2 == 1 ? 
-                        collection.sort( false )[ ( zsize / 2 ).toInteger() ] :
-                        collection.sort( false )[ [ Math.floor( zsize / 2 ), Math.ceil( zsize / 2.0 ) ]*.toInteger() ].sum() / 2
-    double mean     = sum / size
-    double variance = 0
+    if( size == 0 ) {
+      return new AverageStats( mean: 0, median: 0, variance: 0, stdDev: 0 )
+    }
+    V sum             = collection.sum()
+    int zsize         = size - 1
+    BigDecimal median = size % 2 == 1 ?
+                          collection.sort( false )[ ( zsize / 2 ).toInteger() ] :
+                          collection.sort( false )[ [ Math.floor( zsize / 2 ), Math.ceil( zsize / 2.0 ) ]*.toInteger() ].sum() / 2
+    BigDecimal mean   = sum / size
+    BigDecimal variance = 0
 
     for( V num : collection ) {
       variance += ( mean - num ) * ( mean - num )
diff --git a/src/test/groovy/tests/CollectionTests.groovy b/src/test/groovy/tests/CollectionTests.groovy
index b3f2ab5..873f591 100644
--- a/src/test/groovy/tests/CollectionTests.groovy
+++ b/src/test/groovy/tests/CollectionTests.groovy
@@ -144,7 +144,7 @@ class CollectionTests extends Specification {
       def avg = [ 332G, 42G, 100G ].average()
     expect:
       avg.mean     == 158
-      avg.median   == 100G
+      avg.median   == 100
       String.format( '%.7g', avg.variance ) == '15698.67'
       String.format( '%.6g', avg.stdDev )   == '125.294'
   }
@@ -154,8 +154,18 @@ class CollectionTests extends Specification {
       def avg = [ 332.0G, 998.0G, 42.0G, 100.0G ].average()
     expect:
       avg.mean     == 368
-      avg.median   == 216.0G
+      avg.median   == 216
       String.format( '%.7g', avg.variance ) == '144074.0'
       String.format( '%.6g', avg.stdDev )   == '379.571'
   }
+
+  def 'check zero length averages'() {
+    given:
+      def avg = [].average()
+    expect:
+      avg.mean     == 0
+      avg.median   == 0
+      avg.variance == 0
+      avg.stdDev   == 0
+  }
 }
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