Convert array to matrix

Question

I have an array of length m*n that stores a list of double elements.

How to convert it to m*n matrix?

This is the signature of the method.

 //returns a matrix of [m,n], given arr is of length m*n static double[,] ConvertMatrix(Array arr, int m, int n) { } 

Answer 1

You can use Buffer.BlockCopy to do this very efficiently:

 using System; class Test { static double[,] ConvertMatrix(double[] flat, int m, int n) { if (flat.Length != m * n) { throw new ArgumentException("Invalid length"); } double[,] ret = new double[m, n]; // BlockCopy uses byte lengths: a double is 8 bytes Buffer.BlockCopy(flat, 0, ret, 0, flat.Length * sizeof(double)); return ret; } static void Main() { double[] d = { 2, 5, 3, 5, 1, 6 }; double[,] matrix = ConvertMatrix(d, 3, 2); for (int i = 0; i < 3; i++) { for (int j = 0; j < 2; j++) { Console.WriteLine("matrix[{0},{1}] = {2}", i, j, matrix[i, j]); } } } } 

Answer 2

 private static T[,] create2DimArray<T>(T[] array, int n) { if (n <= 0) throw new ArgumentException("Array N dimension cannot be less or equals zero","n"); if (array == null) throw new ArgumentNullException("array", "Array cannot be null"); if (array.Length == 0) throw new ArgumentException("Array cannot be empty", "array"); int m = array.Length % n == 0 ? array.Length / n : array.Length / n + 1; var newArr = new T[m,n]; for (int i = 0; i < arr.Length; i++) { int k = i / n; int l = i % n; newArr[k, l] = array[i]; } return newArr; } 

Answer 3

Create a matrix and loop elements on it:

 static double[,] ConvertMatrix(double[] arr, int m, int n) { double[,] result = new double[m, n]; for (int i = 0; i < arr.Length; i++) { result[i % m, i / m] = arr[i]; } return result; }