LA: create dense matrix from row-major array or enumerable

src/Numerics/LinearAlgebra/Builder.cs

@@ -687,6 +687,17 @@ namespace MathNet.Numerics.LinearAlgebra
             return Dense(DenseColumnMajorMatrixStorage<T>.OfColumnVectors(columns.Select(c => c.Storage).ToArray()));
         }
 
+        /// <summary>
+        /// Create a new dense matrix as a copy of the given enumerable.
+        /// The enumerable is assumed to be in row-major order (row by row).
+        /// This new matrix will be independent from the enumerable.
+        /// A new memory block will be allocated for storing the matrix.
+        /// </summary>
+        public Matrix<T> DenseOfRowMajor(int rows, int columns, IEnumerable<T> columnMajor)
+        {
+            return Dense(DenseColumnMajorMatrixStorage<T>.OfRowMajorEnumerable(rows, columns, columnMajor));
+        }
+
         /// <summary>
         /// Create a new dense matrix as a copy of the given enumerable of enumerable rows.
         /// Each enumerable in the master enumerable specifies a row.

src/Numerics/LinearAlgebra/Storage/DenseColumnMajorMatrixStorage.cs

@@ -266,6 +266,27 @@ namespace MathNet.Numerics.LinearAlgebra.Storage
             return new DenseColumnMajorMatrixStorage<T>(rows, columns, array);
         }
 
+        public static DenseColumnMajorMatrixStorage<T> OfColumnMajorArray(int rows, int columns, T[] data)
+        {
+            T[] ret = new T[rows*columns];
+            Array.Copy(data, 0, ret, 0, Math.Min(ret.Length, data.Length));
+            return new DenseColumnMajorMatrixStorage<T>(rows, columns, ret);
+        }
+
+        public static DenseColumnMajorMatrixStorage<T> OfRowMajorArray(int rows, int columns, T[] data)
+        {
+            T[] ret = new T[rows*columns];
+            for (int i = 0; i < rows; i++)
+            {
+                int offset = i*columns;
+                for (int j = 0; j < columns; j++)
+                {
+                    ret[(j*rows) + i] = data[offset + j];
+                }
+            }
+            return new DenseColumnMajorMatrixStorage<T>(rows, columns, ret);
+        }
+
         public static DenseColumnMajorMatrixStorage<T> OfColumnVectors(VectorStorage<T>[] data)
         {
             if (data.Length <= 0)
@@ -333,14 +354,17 @@ namespace MathNet.Numerics.LinearAlgebra.Storage
             var arrayData = data as T[];
             if (arrayData != null)
             {
-                var copy = new T[arrayData.Length];
-                Array.Copy(arrayData, 0, copy, 0, arrayData.Length);
-                return new DenseColumnMajorMatrixStorage<T>(rows, columns, copy);
+                return OfColumnMajorArray(rows, columns, arrayData);
             }
 
             return new DenseColumnMajorMatrixStorage<T>(rows, columns, data.ToArray());
         }
 
+        public static DenseColumnMajorMatrixStorage<T> OfRowMajorEnumerable(int rows, int columns, IEnumerable<T> data)
+        {
+            return OfRowMajorArray(rows, columns, data as T[] ?? data.ToArray());
+        }
+
         public static DenseColumnMajorMatrixStorage<T> OfColumnEnumerables(int rows, int columns, IEnumerable<IEnumerable<T>> data)
         {
             var array = new T[rows*columns];