Merge pull request #251 from kparrigan/jaccard

Jaccard Distance

src/Numerics/Distance.cs

@@ -388,5 +388,97 @@ namespace MathNet.Numerics
         {
             return 1.0 - Correlation.Pearson(a, b);
         }
+
+        /// <summary>
+        /// Jaccard distance, i.e. 1 - the Jaccard index.
+        /// </summary>
+        /// <exception cref="ArgumentNullException">Thrown if a or b are null.</exception>
+        /// <exception cref="ArgumentException">Throw if a and b are of different lengths.</exception>
+        /// <returns>Jaccard distance.</returns>
+        public static double Jaccard(double[] a, double[] b)
+        {
+            Int32 intersection = 0, union = 0;
+
+            if (a == null)
+            {
+                throw new ArgumentNullException("a");
+            }
+
+            if (b == null)
+            {
+                throw new ArgumentNullException("b");
+            }
+
+            if (a.Length != b.Length)
+            {
+                throw new ArgumentException(Resources.ArgumentVectorsSameLength);
+            }
+
+            if ((a.Length == 0 && b.Length == 0) || (a == null && b == null))
+            {
+                return 0;
+            }
+
+            for (Int32 x = 0, len = a.Length; x < len; x++)
+            {
+                if (a[x] != 0 && b[x] != 0)
+                {
+                    if (a[x] == b[x])
+                    {
+                        intersection++;
+                    }
+
+                    union++;
+                }
+            }
+
+            return 1.0 - ((double)intersection / (double)union);
+        }
+
+        /// <summary>
+        /// Jaccard distance, i.e. 1 - the Jaccard index.
+        /// </summary>
+        /// <exception cref="ArgumentNullException">Thrown if a or b are null.</exception>
+        /// <exception cref="ArgumentException">Throw if a and b are of different lengths.</exception>
+        /// <returns>Jaccard distance.</returns>
+        public static double Jaccard(float[] a, float[] b)
+        {
+            Int32 intersection = 0, union = 0;
+
+            if (a == null)
+            {
+                throw new ArgumentNullException("a");
+            }
+
+            if (b == null)
+            {
+                throw new ArgumentNullException("b");
+            }
+
+            if (a.Length != b.Length)
+            {
+                throw new ArgumentException(Resources.ArgumentVectorsSameLength);
+            }
+
+            if ((a.Length == 0 && b.Length == 0) || (a == null && b == null))
+            {
+                return 0;
+            }
+
+            for (Int32 x = 0, len = a.Length; x < len; x++)
+            {
+                if (a[x] != 0 && b[x] != 0)
+                {
+                    if (a[x] == b[x])
+                    {
+                        intersection++;
+                    }
+
+                    union++;
+                }
+            }
+
+            return 1.0 - ((float)intersection / (float)union);
+        }
     }
 }

src/UnitTests/DistanceTests.cs

@@ -1,4 +1,5 @@
 using NUnit.Framework;
+using System;
 
 namespace MathNet.Numerics.UnitTests
 {
@@ -15,5 +16,71 @@ namespace MathNet.Numerics.UnitTests
             Assert.That(Distance.Hamming(new[] { 0.0, 0.0 }, new[] { 1.0, 1.0 }), Is.EqualTo(2.0));
             Assert.That(Distance.Hamming(new[] { 1.0, 0.0 }, new[] { 0.0, 1.0 }), Is.EqualTo(2.0));
         }
+
+        [Test]
+        public void Jaccard_Double()
+        {
+            double[] p0 = new double[] { 1, 0.5 };
+            double[] q0 = new double[] { 0.5, 1 };
+
+            double[] p1 = new double[] { 4.5, 1 };
+            double[] q1 = new double[] { 4, 2 };
+
+            double[] p2 = new double[] { 0, 0, 0 };
+            double[] q2 = new double[] { 0, 0, 0 };
+
+            double[] p3 = new double[] { 1, 1, 1 };
+            double[] q3 = new double[] { 1, 1, 1 };
+
+            double[] p4 = new double[] { 2.5, 3.5, 3.0, 3.5, 2.5, 3.0 };
+            double[] q4 = new double[] { 3.0, 3.5, 1.5, 5.0, 3.5, 3.0 };
+
+            double[] p5 = new double[] { 1, 3, 5, 6, 8, 9, 6, 4, 3, 2 };
+            double[] q5 = new double[] { 2, 5, 6, 6, 7, 7, 5, 3, 1, 1 };
+
+            Assert.Throws<ArgumentException>(() => Distance.Jaccard(p0, q4));
+            Assert.Throws<ArgumentNullException>(() => Distance.Jaccard(null, q4));
+            Assert.Throws<ArgumentNullException>(() => Distance.Jaccard(p0, null));
+
+            Assert.That(Distance.Jaccard(p0, q0), Is.EqualTo(1));
+            Assert.That(Distance.Jaccard(p1, q1), Is.EqualTo(1));
+            Assert.That(Distance.Jaccard(p2, q2), Is.EqualTo(Double.NaN));
+            Assert.That(Distance.Jaccard(p3, q3), Is.EqualTo(0));
+            Assert.That(Distance.Jaccard(p4, q4), Is.EqualTo(0.66666).Within(0.00001));
+            Assert.That(Distance.Jaccard(p5, q5), Is.EqualTo(0.9).Within(0.1));
+        }
+
+        [Test]
+        public void Jaccard_Float()
+        {
+            float[] p0 = new float[] { 1, 0.5f };
+            float[] q0 = new float[] { 0.5f, 1 };
+
+            float[] p1 = new float[] { 4.5f, 1 };
+            float[] q1 = new float[] { 4, 2 };
+
+            float[] p2 = new float[] { 0, 0, 0 };
+            float[] q2 = new float[] { 0, 0, 0 };
+
+            float[] p3 = new float[] { 1, 1, 1 };
+            float[] q3 = new float[] { 1, 1, 1 };
+
+            float[] p4 = new float[] { 2.5f, 3.5f, 3.0f, 3.5f, 2.5f, 3.0f };
+            float[] q4 = new float[] { 3.0f, 3.5f, 1.5f, 5.0f, 3.5f, 3.0f };
+
+            float[] p5 = new float[] { 1, 3, 5, 6, 8, 9, 6, 4, 3, 2 };
+            float[] q5 = new float[] { 2, 5, 6, 6, 7, 7, 5, 3, 1, 1 };
+
+            Assert.Throws<ArgumentException>(() => Distance.Jaccard(p0, q4));
+            Assert.Throws<ArgumentNullException>(() => Distance.Jaccard(null, q4));
+            Assert.Throws<ArgumentNullException>(() => Distance.Jaccard(p0, null));
+
+            Assert.That(Distance.Jaccard(p0, q0), Is.EqualTo(1));
+            Assert.That(Distance.Jaccard(p1, q1), Is.EqualTo(1));
+            Assert.That(Distance.Jaccard(p2, q2), Is.EqualTo(float.NaN));
+            Assert.That(Distance.Jaccard(p3, q3), Is.EqualTo(0));
+            Assert.That(Distance.Jaccard(p4, q4), Is.EqualTo(0.66666).Within(0.00001));
+            Assert.That(Distance.Jaccard(p5, q5), Is.EqualTo(0.9).Within(0.1));
+        }
     }
 }