public void SelectByColumnIndicesTest()
{
Matrix.Deco().Says("rows");
Matrix.SelectColumns(Seq.From(1, 2, 4)).Deco().Says("selected");
Matrix.SelectRows(Seq.From(1, 2, 4)).Deco().Says("selected");
SymmetricMatrix.SelectBy(Matrix, Seq.From(1, 2, 4)).Deco().Says("symmetric selected");
SymmetricMatrix.LowerTriangular(Matrix).Map(x => x ?? "").Deco().Says("lower triangular");
SymmetricMatrix.UpperTriangular(Matrix).Map(x => x ?? "").Deco().Says("upper triangular");
}