From 8fb1d36f73a88a3cc52402fae7d7a1a8444561e2 Mon Sep 17 00:00:00 2001
From: Christoph Ruegg <git@cdrnet.ch>
Date: Thu, 21 Mar 2013 14:03:32 +0100
Subject: [PATCH] Statistics: never throw on empty data (instead use NaN)

---
 src/Numerics/Statistics/Statistics.cs         | 43 ++++++-------------
 .../StatisticsTests/StatisticsTests.cs        | 16 +++++--
 2 files changed, 27 insertions(+), 32 deletions(-)

diff --git a/src/Numerics/Statistics/Statistics.cs b/src/Numerics/Statistics/Statistics.cs
index 9a957609..ec992a11 100644
--- a/src/Numerics/Statistics/Statistics.cs
+++ b/src/Numerics/Statistics/Statistics.cs
@@ -344,12 +344,7 @@ namespace MathNet.Numerics.Statistics
                 }
             }
 
-            if (count == 0)
-            {
-                throw new ArgumentException(Resources.CollectionEmpty, "data");
-            }
-
-            return min;
+            return count == 0 ? double.NaN : min;
         }
 
         /// <summary>
@@ -375,12 +370,7 @@ namespace MathNet.Numerics.Statistics
                 }
             }
 
-            if (count == 0)
-            {
-                throw new ArgumentException(Resources.CollectionEmpty, "data");
-            }
-
-            return max;
+            return count == 0 ? double.NaN : max;
         }
 
         /// <summary>
@@ -403,12 +393,7 @@ namespace MathNet.Numerics.Statistics
                 count++;
             }
 
-            if (count == 0)
-            {
-                throw new ArgumentException(Resources.CollectionEmpty, "data");
-            }
-
-            return min;
+            return count == 0 ? double.NaN : min;
         }
 
         /// <summary>
@@ -431,12 +416,7 @@ namespace MathNet.Numerics.Statistics
                 count++;
             }
 
-            if (count == 0)
-            {
-                throw new ArgumentException(Resources.CollectionEmpty, "data");
-            }
-
-            return max;
+            return count == 0 ? double.NaN : max;
         }
 
         /// <summary>
@@ -452,6 +432,11 @@ namespace MathNet.Numerics.Statistics
             }
 
             var dataArray = new List<double>(data);
+            if (dataArray.Count == 0)
+            {
+                return double.NaN;
+            }
+
             int index = (dataArray.Count / 2) + 1;
             if (dataArray.Count % 2 == 0)
             {
@@ -484,11 +469,6 @@ namespace MathNet.Numerics.Statistics
                 }
             }
 
-            if (nonNull.Count == 0)
-            {
-                throw new ArgumentException(Resources.CollectionEmpty, "data");
-            }
-
             return nonNull.Median();
         }
 
@@ -507,6 +487,11 @@ namespace MathNet.Numerics.Statistics
             }
 
             var list = new List<double>(samples);
+            if (list.Count == 0)
+            {
+                return double.NaN;
+            }
+
             if (order < 1 || order > list.Count)
             {
                 throw new ArgumentOutOfRangeException("order", Resources.ArgumentInIntervalXYInclusive);
diff --git a/src/UnitTests/StatisticsTests/StatisticsTests.cs b/src/UnitTests/StatisticsTests/StatisticsTests.cs
index 9e924303..22e772bc 100644
--- a/src/UnitTests/StatisticsTests/StatisticsTests.cs
+++ b/src/UnitTests/StatisticsTests/StatisticsTests.cs
@@ -63,6 +63,11 @@ namespace MathNet.Numerics.UnitTests.StatisticsTests
             Assert.Throws<ArgumentNullException>(() => Statistics.Minimum(data));
             Assert.Throws<ArgumentNullException>(() => Statistics.Maximum(data));
             Assert.Throws<ArgumentNullException>(() => Statistics.Mean(data));
+            Assert.Throws<ArgumentNullException>(() => Statistics.Median(data));
+            Assert.Throws<ArgumentNullException>(() => Statistics.Variance(data));
+            Assert.Throws<ArgumentNullException>(() => Statistics.StandardDeviation(data));
+            Assert.Throws<ArgumentNullException>(() => Statistics.PopulationVariance(data));
+            Assert.Throws<ArgumentNullException>(() => Statistics.PopulationStandardDeviation(data));
 
             Assert.Throws<ArgumentNullException>(() => SortedArrayStatistics.Minimum(data));
             Assert.Throws<ArgumentNullException>(() => SortedArrayStatistics.Maximum(data));
@@ -88,9 +93,14 @@ namespace MathNet.Numerics.UnitTests.StatisticsTests
         {
             double[] data = new double[0];
 
-            //Assert.DoesNotThrow(() => Statistics.Minimum(data));
-            //Assert.DoesNotThrow(() => Statistics.Maximum(data));
-            //Assert.DoesNotThrow(() => Statistics.Mean(data));
+            Assert.DoesNotThrow(() => Statistics.Minimum(data));
+            Assert.DoesNotThrow(() => Statistics.Maximum(data));
+            Assert.DoesNotThrow(() => Statistics.Mean(data));
+            Assert.DoesNotThrow(() => Statistics.Median(data));
+            Assert.DoesNotThrow(() => Statistics.Variance(data));
+            Assert.DoesNotThrow(() => Statistics.StandardDeviation(data));
+            Assert.DoesNotThrow(() => Statistics.PopulationVariance(data));
+            Assert.DoesNotThrow(() => Statistics.PopulationStandardDeviation(data));
 
             Assert.DoesNotThrow(() => SortedArrayStatistics.Minimum(data));
             Assert.DoesNotThrow(() => SortedArrayStatistics.Maximum(data));