/// <summary>
/// Initializes a new instance of <see cref="TriangularLower"/> by copying the lower triangle of the provided 2D array.
/// </summary>
/// <param name="array2D">A 2-dimensional array containing the elements of the matrix. Constraints:
/// <paramref name="array2D"/>.GetLength(0) == <paramref name="array2D"/>.GetLength(1).</param>
/// <exception cref="NonMatchingDimensionsException">Thrown if <paramref name="array2D"/>.GetLength(0) !=
/// <paramref name="array2D"/>.GetLength(1).</exception>
public static TriangularLower CreateFromArray(double[,] array2D)
{
int numRows = array2D.GetLength(0);
int numCols = array2D.GetLength(1);
if (numRows != numCols)
{
string msg = $"Provided array must have the same dimensions, but was ({numRows}x{numCols})";
throw new NonMatchingDimensionsException(msg);
}
return(new TriangularLower(Conversions.Array2DToPackedLowerRowMajor(array2D), numRows));
}