LA: Initialize sparse vector by enumerable #104

src/Numerics/LinearAlgebra/Complex/SparseVector.cs

@@ -119,17 +119,13 @@ namespace MathNet.Numerics.LinearAlgebra.Complex
         }
 
         /// <summary>
-        /// Create a new sparse vector as a copy of the given array.
-        /// This new vector will be independent from the array.
+        /// Create a new sparse vector as a copy of the given enumerable.
+        /// This new vector will be independent from the enumerable.
         /// A new memory block will be allocated for storing the vector.
         /// </summary>
-        public SparseVector(IList<Complex> array)
-            : this(new SparseVectorStorage<Complex>(array.Count))
+        public SparseVector(IEnumerable<Complex> other)
+            : this(SparseVectorStorage<Complex>.FromEnumerable(other))
         {
-            for (var i = 0; i < array.Count; i++)
-            {
-                Storage.At(i, array[i]);
-            }
         }
 
         /// <summary>

src/Numerics/LinearAlgebra/Complex32/SparseVector.cs

@@ -119,17 +119,13 @@ namespace MathNet.Numerics.LinearAlgebra.Complex32
         }
 
         /// <summary>
-        /// Create a new sparse vector as a copy of the given array.
-        /// This new vector will be independent from the array.
+        /// Create a new sparse vector as a copy of the given enumerable.
+        /// This new vector will be independent from the enumerable.
         /// A new memory block will be allocated for storing the vector.
         /// </summary>
-        public SparseVector(IList<Complex32> array)
-            : this(new SparseVectorStorage<Complex32>(array.Count))
+        public SparseVector(IEnumerable<Complex32> other)
+            : this(SparseVectorStorage<Complex32>.FromEnumerable(other))
         {
-            for (var i = 0; i < array.Count; i++)
-            {
-                Storage.At(i, array[i]);
-            }
         }
 
         /// <summary>

src/Numerics/LinearAlgebra/Double/SparseVector.cs

@@ -119,17 +119,13 @@ namespace MathNet.Numerics.LinearAlgebra.Double
         }
 
         /// <summary>
-        /// Create a new sparse vector as a copy of the given array.
-        /// This new vector will be independent from the array.
+        /// Create a new sparse vector as a copy of the given enumerable.
+        /// This new vector will be independent from the enumerable.
         /// A new memory block will be allocated for storing the vector.
         /// </summary>
-        public SparseVector(IList<double> array)
-            : this(new SparseVectorStorage<double>(array.Count))
+        public SparseVector(IEnumerable<double> other)
+            : this(SparseVectorStorage<double>.FromEnumerable(other))
         {
-            for (var i = 0; i < array.Count; i++)
-            {
-                Storage.At(i, array[i]);
-            }
         }
 
         /// <summary>

src/Numerics/LinearAlgebra/Single/SparseVector.cs

@@ -119,17 +119,13 @@ namespace MathNet.Numerics.LinearAlgebra.Single
         }
 
         /// <summary>
-        /// Create a new sparse vector as a copy of the given array.
-        /// This new vector will be independent from the array.
+        /// Create a new sparse vector as a copy of the given enumerable.
+        /// This new vector will be independent from the enumerable.
         /// A new memory block will be allocated for storing the vector.
         /// </summary>
-        public SparseVector(IList<float> array)
-            : this(new SparseVectorStorage<float>(array.Count))
+        public SparseVector(IEnumerable<float> other)
+            : this(SparseVectorStorage<float>.FromEnumerable(other))
         {
-            for (var i = 0; i < array.Count; i++)
-            {
-                Storage.At(i, array[i]);
-            }
         }
 
         /// <summary>

src/Numerics/LinearAlgebra/Storage/SparseVectorStorage.cs

@@ -282,6 +282,37 @@ namespace MathNet.Numerics.LinearAlgebra.Storage
             return hash;
         }
 
+        // INITIALIZATION
+
+        public static SparseVectorStorage<T> FromEnumerable(IEnumerable<T> data)
+        {
+            if (data == null)
+            {
+                throw new ArgumentNullException("data");
+            }
+
+            var indices = new List<int>();
+            var values = new List<T>();
+            int length = 0;
+
+            foreach (T item in data)
+            {
+                if (!Zero.Equals(item))
+                {
+                    values.Add(item);
+                    indices.Add(length);
+                }
+                length++;
+            }
+
+            return new SparseVectorStorage<T>(length)
+                {
+                    Indices = indices.ToArray(),
+                    Values = values.ToArray(),
+                    ValueCount = values.Count
+                };
+        }
+
         // ENUMERATION
 
         public override IEnumerable<T> Enumerate()